# Milling Metals With a Router



## RWoody

After a little delay, and kindly been directed to the metalworking section by Charley _(I hadn't noticed there was one, to be honest  )_ I'm now putting out a request for some expertise on the subject of milling using a router. I have already discussed this a little on the woodworking part of this site (with some helpful comments I must say) but being a very cautious guy, I'd like to put it out to a wider audience too:

Has, or have, any of you used a router to mill metal with? I'm talking brass in my case. The concerns I have are ones of head rotation speed, as a usual metalworking lathe operates at low rpms in the region of 600, for example, whereas a router, designed primarily for wood, spins at many, many times that, often around the 20,000 rpm mark. While I doubt the router wouldn't cut metal, my main concern is heat. Surely, even if using cutting lubrication _(and much would 'spray' off too at these high router bit speeds)_ things will heat up rapidly, and take off the router bit's temper?

Secondly, because of the fast speed a router has, would not the cutting surfaces become dull quickly too? I mean one isn't going to be able to sharpen a TCT cutter themselves anyway _(though correct me if I'm wrong)_ as they aren't 'soft' like HSS, which can be sharpened, but I'm sure would become dull VERY quickly if milling metal!? 

So is there anyone who has first hand experience with this, who'd be able to give a bit of sound advice, please? Thanks in advance. :0)


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## bugbear

I've heard of people juu...uust getting away with working aluminium with WW tools, e.g. bandsaw or router, but it's a stop gap.

Brass is well beyond the limit, I suspect.

BugBear


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## mseries

I've been reading up on this myself recently, not for brass but for 2mm aluminium. It does seem do able. Heat seems to be the main worry and run your router slower, mine are speed adjustable. I don't have first hand experience (yet) but my mate Aiden said he's done it (Aiden is like Emmet Brown though). I am confident enough to give it a try, I'll make a good jig/holder to hold my workpiece, I am not sure though if I should use my router inverted in my table or clamp the workpiece and move the router. I'm thinking the latter so my cutting fluid/coolant will not run into the router nor will the swarf.


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## Spindle

Hi

You need to consider the cutting speed of the tool - see the chart in the link attached:

http://www.littlemachineshop.com/Refere ... Speeds.php

Using these figures a 1/2" diameter carbide tool cutting brass would require a rotational speed of 8,900 rpm - well within the range of a variable speed router.

I wouldn't suggest using a router for deep sections, its just not powerful enough, but for cuts of 2 or 3mm deep in brass and aluminium it should be fine.

Obviously you will need to secure the work well, wear eye and ear protection, traverse the router in a steady and controlled manner and take light cuts.

Regards Mick


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## RWoody

Thank you both for this. It kind of confirms my concerns, though not entirely, as it does seem that with very soft metals, such as aluminium, it's possible, at a squeeeeeze! I think I can rule brass out now, it would seem :-(

IF I were to try milling in this fashion I would use my WoodRat, is it'd be ideal for working along in a straight line with good linear and lateral control. It still doesn't get over the 'heat' issue though, in my view; and as you say, there is the issue of ingress of coolant into the bearings of the router, if inverted - quite aside from the 'spray' issue.


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## Spindle

Hi

Why would you rule out brass?

Regards Mick


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## RWoody

Thanks Spindle, your reply came in while I was typing a response to the other two contributors.

The site in the hyperlink looks interesting, but it only serves to send alarm bells in my head, regarding speed, depth and material etc. So, in light of all I've heard so far, and now you 3 guys, I'm seriously thinking of an alternative material entirely. 

You see, what I'm after is a mitre guide, which will fit my rather small guide grooves _(as per Mike's excellent review of mitre guides on this website)_ as the Incra I'm now after has a guide width that's much larger than both of my saw table ones _(one is for a circular saw and the other a bandsaw)_ and EACH of my two machines has a different depth and width guide grooves in the tables. I was therefore originally hoping to make up some metal strips to fit the bottom of the Incra's guide; one for each table. As I have some brass strips, I was hoping to use those. However, I can't see that practically happening now, in light of these information I've gleaned from this forum, which only served to compound my belief that it wasn't really the way to go.

So I'm now wondering about either a very hard wood OR maybe some sort of Bakelite or some other hard man-made material. I can then put some pins upwards in these strips, to engage with the holes I shall drill into the Incra's guide _(being careful not to weaken it too much of course)_. Anyway, I'm sort of gradually coming to an undesrstanding of what I need to to do, and with what material _(if I can get hold of it)_. 

Thanks again Spindle.


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## RWoody

Spindle":3vlpf7sd said:


> Hi
> 
> Why would you rule out brass?
> 
> Regards Mick



I'd rule out brass because it's harder than aluminium; and if it's debatable to even to try with aluminium, then brass will definitely be out. That's all.


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## mseries

RWoody":zzs1yl43 said:


> some sort of Bakelite or some other hard man-made material. .... _(if I can get hold of it)_.



There is lots of acrylic/perspex/plexiglas/lexan as well as phenolic on eBay


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## RWoody

mseries":b7go2150 said:


> RWoody":b7go2150 said:
> 
> 
> 
> some sort of Bakelite or some other hard man-made material. .... _(if I can get hold of it)_.
> 
> 
> 
> 
> There is lots of acrylic/perspex/plexiglas/lexan as well as phenolic on eBay
Click to expand...


That's true. Funny, but I buy loads of stuff from eBay, so not sure why I believed I had to source it from a specialist. Thanks anyway!


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## Cheshirechappie

RWoody":hj5iy98k said:


> You see, what I'm after is a mitre guide, which will fit my rather small guide grooves _(as per Mike's excellent review of mitre guides on this website)_ as the Incra I'm now after has a guide width that's much larger than both of my saw table ones _(one is for a circular saw and the other a bandsaw)_ and EACH of my two machines has a different depth and width guide grooves in the tables. I was therefore originally hoping to make up some metal strips to fit the bottom of the Incra's guide; one for each table. As I have some brass strips, I was hoping to use those. However, I can't see that practically happening now, in light of these information I've gleaned from this forum, which only served to compound my belief that it wasn't really the way to go.



The metalworker's way to fit a strip to an existing groove is to file it to fit. Use a turnip file to remove the bulk of the waste, then 'creep up' on a fit with second-cut and finally smooth files. Check frequently with a straightedge and small engineer's square that you're filing straight, and try the fit frequently once you're close. Hold the brass strip in a vice, and use both hands on the file. This will be quicker than you think - brass files easily, especially with a nice sharp new file. Do a 'practice run' with a short strip if you've not tried this before.

Even if you milled the strip to width, you'd have to do the final fitting with files to avoid a sloppy fit. Even on a 'proper' milling machine, getting a smooth sliding fit straight off the machine is pretty unlikely - it'll be close, but either a bit sloppy (fail - scrap) or a bit tight (ease fit with smooth file). [Production guys will get a reasonable fit from the machine, but they'll need a couple of practice runs to refine settings. Better class work is almost always 'fitted' by hand after machining, especially in the case of 'one-offs'.]


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## wizard

I would not even think about it the item must be held so there is no movement, milling cutters break very easy, I would not even use a cheap modern milling machine; there are loads of them that have only been used a few times. I have two very old milling machines that work well but you have to know what you are doing.


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## n0legs

:?:


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## jasonB

Spindle":3jobmtet said:


> Hi
> 
> You need to consider the cutting speed of the tool - see the chart in the link attached:
> 
> http://www.littlemachineshop.com/Refere ... Speeds.php
> 
> Using these figures a 1/2" diameter carbide tool cutting brass would require a rotational speed of 8,900 rpm - well within the range of a variable speed router.
> 
> I wouldn't suggest using a router for deep sections, its just not powerful enough, but for cuts of 2 or 3mm deep in brass and aluminium it should be fine.
> 
> Obviously you will need to secure the work well, wear eye and ear protection, traverse the router in a steady and controlled manner and take light cuts.
> 
> Regards Mick




How do you get 8,900rpm? that's way too fast.

Using the max for milling brass on that table the speed is 200fpm or 2400inches per min. A 1/2" cutter has a circumference of about 1.6" so 2400/1.6 = 1500rpm, definately not within any routers speed range that I can think of.

Also brass is cut dry so not lubrication to worryabout though I would still not do it.

J


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## SteveW1000

Aluminium doors and windows have holes for hinges and locks routed, Trend list high speed cutters for this purpose. Brass should be possible with a smaller diameter cutter which would lower the surface speed. What I would question is how you intend to hold the metal while routing it, I'm not sure how this could be done safely.

Regards

Steve

Sent from my ST23i using Tapatalk


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## Eric The Viking

I've milled brass very successfully on a router table, using a standard woodwork carbide chamfer cutter (45 degree bevel).

I was converting a straight plumbing spigot into a compression fitting, by machining an accurate 60-degree bevel on the inside edge of the end. I had to accurately tilt the workpiece 15 degrees and work out how to address it properly with the cutter, but it all worked out fine.

It was a while ago, and my memory is a bit hazy, but several things occur to me:

1. Make sure you have enough stock to experiment with.

2. I *think* I used a high speed (flat out on my T11). See speed calc below..

3. I took very gentle passes, that's partly because the result needed to be very precise (otherwise it would leak!), but also I didn't want to stress the cutter nor the workpiece.

4. Think of how a proper lathe or milling machine works: you need a way of advancing the cutter in tiny increments. I strongly suggest some sort of jig, with the ability to micro-advance the workpiece. For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch). 

The amount of advance was determined mainly by listening. I couldn't see the cut at all, as it was guarded, so I'd start with it off the workpiece, move it in until just cutting, make a complete pass and back the cutter off again, stop the router and inspect (takes longer to write than to actually do!). The scale on the Trend-supplied box spanner for height adjustment (0.10mm increments) was invaluable: each cut meant the next would start at a different 'depth', so one needed to remember where one got to the previous time. 

5. Obviously, this was done 'dry'. Vacuum extraction is essential, as the brass comes off as chips, not turned swarf. These are very sharp-edged, and get everywhere if not immediately contained. You need several soft brushes you're prepared to dispose of AND to make sure the work area is fully degreased to prevent the chips sticking. I was terrified they'd get into the router*, but the airflow from it is upwards, and as far as I can tell nothing got in. 

I strongly advise stopping fairly frequently and cleaning up. Don't work on any wooden surface like a bench, as you'll have a terrible time getting rid of the chips that have worked into the surface, and if you don't they'll wreck any finished woodwork that touches the surface later. I used a crevice nozzle on my workshop vacuum to extract as close to the action as physically possible and get a really fast airflow, and deliberately didn't clean the filter after the previous woodwork job (although I did empty it). The brass chips buried themselves in the sawdust on the filter and didn't get to the cloth, or the motor. I blew the filter out after use.

6. When planning the job, think of the clear-up and extraction needed first, and work backwards to the actual cutting process.

7. Be analytical: There are cutting speed tables available for working brass. You can work out the cutting speeds for a given cutter and router setting: say your cutter is 1/2" (say 12.5mm), and the router speed is 20,000 RPM:


Code:


20,000 RPM is around 333 revs. per sec.
cutter circumference is PI x 12.5...     = 39.3mm
so           cutter speed is 13,089 mm/sec

You can work this out for whatever cutter you're using and adjust the speed accordingly. If you're cutting at the right speed, it's one less problem to deal with if the results are poor.

8. Vibration is your enemy, too. At the speed I was working, I was essentially thumping the brass 40,000 times per minute. If you can't hold the router and the workpiece rock steady (and advance the cutter or workpiece slowly) don't do it. I wouldn't think about anything hand-held, unless I was able to screw down or really heavily clamp the stock. Even then be prepared for poor results. 

I was working on small (1") pipe fittings, so a handheld router was quite undesirable, but I'd still think twice about it for bigger jobs. The router table isn't ideal, as it risks damaging the router internals, but with really strong extraction, it worked for me.
. . .

The results exceeded my expectations. I now have two completely non-standard-size fittings coupling my boiler to the rest of the heating system. I have eliminated two very expensive and _totally_ useless "service valves," after the third pair leaked in the same way as the earlier two. I will never, ever buy that brand of boiler again.

Hope that's not too 'bossy' above. Brass shouldn't need lubrication when it's being milled, so a router can do it pretty well. I've also done aluminium a couple of times, but the results weren't as good.

E.

*like almost all motors, a router's motor coils are enamelled copper wire. Anything that cuts through the enamel has the potential to short out turns of the winding, leading to the motor burning out (end of router, probably). I was taking a big risk in that regard!


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## Harbo

I routed the edges of this plane 







Using a slow speed on my router table and held freehand.

Rod


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## Eric The Viking

Harbo":3carqz1s said:


> I routed the edges of this plane
> 
> 
> 
> 
> 
> 
> Using a slow speed on my router table and held freehand.
> 
> Rod



Really nice! 

I sit corrected on the freehand thing, but did it vibrate a lot and how much finishing did you have to do afterwards?

E.


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## jasonB

> 20,000 RPM is around 333 revs. per sec.
> cutter circumference is PI x 12.5... = 39.3mm
> so cutter speed is 13,089 mm/sec



Again really is too fast thats something like 2500FPM when suggested speeds for brass are 200FPM!!


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## Eric The Viking

jasonB":2kyyccki said:


> 20,000 RPM is around 333 revs. per sec.
> cutter circumference is PI x 12.5... = 39.3mm
> so cutter speed is 13,089 mm/sec
> 
> 
> 
> 
> Again really is too fast thats something like 2500FPM when suggested speeds for brass are 200FPM!!
Click to expand...


That was rather my point - I can't remember what I used, but you can easily calculate it so you're in the ballpark.


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## graduate_owner

Rwoody:
do you know of any metalworkers in your area? (Probably not else you would already have tried them) Perhaps a look on a metalwork forum might bring up a new acquaintance? Doing the bulk of the work on a milling machine and finishing off by hand filing sounds the best and safest way to me.

K


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## Spindle

Hi

Per my original post, and in response to JasonB - the cutting speeds are considerably higher for carbide tooling, see attached:

http://www.niagaracutter.com/solidcarbi ... dfeed.html

Well within the speed range of most variable speed routers

Regards Mick


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## Racers

I milled the slot and round overs with a router, milling cutter for the slot and normal 1/4" shank round over bit for the edges.







Pete


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## DTR

Eric The Viking":33fmj2qw said:


> For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch).



Being pedantic here, M8 has a pitch of 1.25mm. M6 has a pitch of 1mm :wink:


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## Gerry

DTR":1fkjdirr said:


> Eric The Viking":1fkjdirr said:
> 
> 
> 
> For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch).
> 
> 
> 
> 
> Being pedantic here, M8 has a pitch of 1.25mm. M6 has a pitch of 1mm :wink:
Click to expand...


Also being pedantic, Common M8 pitches are 1.25mm or 1.5mm (fine or course)

Gerry


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## Myfordman

Gerry":16e5pein said:


> DTR":16e5pein said:
> 
> 
> 
> 
> 
> Eric The Viking":16e5pein said:
> 
> 
> 
> For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch).
> 
> 
> 
> 
> Being pedantic here, M8 has a pitch of 1.25mm. M6 has a pitch of 1mm :wink:
> 
> Click to expand...
> 
> 
> Also being pedantic, Common M8 pitches are 1.25mm or 1.5mm (fine or course)
> 
> Gerry
Click to expand...



In extra-pedant mode on both accuracy and spelling! (grin) 
I think M8 x 1.25 is the iso metric coarse standard???

MM


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## Eric The Viking

Oooh Arr.

'twas a simple mistake originally anyway. The point being "some way of micro-adjusting"

I have Zeus tables* too - just didn't have them handy.

E.

* well a Presto Counsellor - same difference.


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## DTR

Gerry":2splikeu said:


> DTR":2splikeu said:
> 
> 
> 
> 
> 
> Eric The Viking":2splikeu said:
> 
> 
> 
> For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch).
> 
> 
> 
> 
> Being pedantic here, M8 has a pitch of 1.25mm. M6 has a pitch of 1mm :wink:
> 
> Click to expand...
> 
> 
> Also being pedantic, Common M8 pitches are 1.25mm or 1.5mm (fine or course)
> 
> Gerry
Click to expand...


Touché :lol:


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## ss03947

> do you know of any metalworkers in your area? (Probably not else you would already have tried them) Perhaps a look on a metalwork forum might bring up a new acquaintance? Doing the bulk of the work on a milling machine and finishing off by hand filing sounds the best and safest way to me.



Woody, what's quoted in the post above, there's got to be a small workshop near by.

I've seen many an accident with milling machines never mind a router.. :shock: ..vibration is your worst enemy.

SS.


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## RWoody

Wow, thanks for all the contributions guys. I've literally just come back to the forum, as I've been away on other work the past week or so, and I see quite a few posts to catch up on. I'll come back to each of you when I've read through completely. Thanks again, much appreciated!


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## RWoody

Cheshirechappie":294zwutj said:


> The metalworker's way to fit a strip to an existing groove is to file it to fit. Use a turnip file to remove the bulk of the waste, then 'creep up' on a fit with second-cut and finally smooth files. Check frequently with a straightedge and small engineer's square that you're filing straight, and try the fit frequently once you're close. Hold the brass strip in a vice, and use both hands on the file. This will be quicker than you think - brass files easily, especially with a nice sharp new file. Do a 'practice run' with a short strip if you've not tried this before.
> 
> Even if you milled the strip to width, you'd have to do the final fitting with files to avoid a sloppy fit. Even on a 'proper' milling machine, getting a smooth sliding fit straight off the machine is pretty unlikely - it'll be close, but either a bit sloppy (fail - scrap) or a bit tight (ease fit with smooth file). [Production guys will get a reasonable fit from the machine, but they'll need a couple of practice runs to refine settings. Better class work is almost always 'fitted' by hand after machining, especially in the case of 'one-offs'.]


[/quote]

I agree with what you're saying, when one gets near to the ideal size. I have already used a couple of files, with great success; but where this just isn't practical, is when there is a much more to take off. It'd take forever to file, which is why I was looking at another solution, and hence the router milling question.

I'm actually minded to cut, with a fine-toothed hacksaw, to remove the bulk; then to finish off with files as you suggest. In the end this might well be the best solution, though I shall read through the other responses first, just to _see_ if there are any other ideas. Thanks.


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## RWoody

wizard":301m494l said:


> I would not even think about it the item must be held so there is no movement, milling cutters break very easy, I would not even use a cheap modern milling machine; there are loads of them that have only been used a few times. I have two very old milling machines that work well but you have to know what you are doing.



Good point, and something that's easily overlooked. This is one of the reasons why I found it necessary to put the question out there: so many aspects to think of, and some possible solutions, but sometimes difficult to implement for the reason you state. It doesn't help me in this case, other than putting me off from using the said power tool, but just goes into the many things one needs to think about. Thanks wizard.


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## RWoody

n0legs":1p1j0jfn said:


> I used my router once on aluminium.
> It cut quite well until a chip of aluminium ended up in the motor shorting it out.
> It was still under warranty so the repair cost me nothing except an explanation on how metal ended up inside it.
> My advice if you do try. Cover the ventilation holes near the collet and allow the machine to cool down a few times during use. Better still find a machine shop to do it for you.



Thanks n0legs. One to think about if going this route!


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## RWoody

SteveW1000":1o20uasa said:


> Aluminium doors and windows have holes for hinges and locks routed, Trend list high speed cutters for this purpose. Brass should be possible with a smaller diameter cutter which would lower the surface speed. What I would question is how you intend to hold the metal while routing it, I'm not sure how this could be done safely.



Good point, Steve. Also I'd 'hold' the router in my WoodRat. I think this would be a more secure way of holding the router itself.


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## RWoody

I've 'quoted' but deleted your body text as it'd have taken a huge amount of space; but at least you know who I'm referring to 

What an extensive, informative post, Eric! I genuinely appreciate it, having read every word. I also find the 'risks' _(the metal 'chips' as opposed to swarf etc.)_, as well as the 'cautions' _(finding a way to very slowly, and accurately advance the cutters)_ understandable, but at the same time concerning, as although I'd use my WoodRat IF I was to go this route, I'm thinking about how to prepare to amply rectify these issues? I'm really leaning towards an earlier comment I made, where I'd employ both a hacksaw AND files.

Thanks again, Eric.


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## wizard

just buy a milling machine, simples.


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## RWoody

Harbo":2gbrbh19 said:


> I routed the edges of this plane
> 
> 
> 
> 
> 
> 
> 
> Using a slow speed on my router table and held freehand.
> 
> Rod



Looks beautiful, Harbo! I presume you did it for the visual impact as opposed to functional improvement in some way?


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## RWoody

graduate_owner":tbrq6e14 said:


> Rwoody:
> do you know of any metalworkers in your area? (Probably not else you would already have tried them) Perhaps a look on a metalwork forum might bring up a new acquaintance? Doing the bulk of the work on a milling machine and finishing off by hand filing sounds the best and safest way to me.
> 
> K



Hi K,

Your assumption is correct: I don't know any metalworkers in my area, no. There must be some, but I haven't checked - though I could run through the members on the forum, to see if any are. I'm sure the guy who sadly passed away, and whose tools and machinery I now have, would have been able to help point me in the right direction. Apart from his knowledge, he was a true craftsmen _(my father's best buddy, and my metalwork teacher as senior school many years ago)_. There is even a group on YouTube, dedicated to his model steam traction engines! Also the Americans actually copied and printed one of his books, in woodwork, without his permission. He later sought, and got recompense.

Thanks for your input.


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## RWoody

Spindle":fw6omotu said:


> Hi
> 
> Per my original post, and in response to JasonB - the cutting speeds are considerably higher for carbide tooling, see attached:
> 
> http://www.niagaracutter.com/solidcarbi ... dfeed.html
> 
> Well within the speed range of most variable speed routers
> 
> Regards Mick



Thanks Spindle; it'll be good for future reference. I'm bookmarking it!


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## RWoody

Racers":10x0y94g said:


> I milled the slot and round overs with a router, milling cutter for the slot and normal 1/4" shank round over bit for the edges.
> 
> 
> 
> 
> 
> 
> 
> Pete



Looks a really professional job indeed, Pete. Attaching images of work you've actually done, really does demonstrate well what can be achieved, with care. Thanks a lot!


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## RWoody

Gerry":1p2hjcip said:


> DTR":1p2hjcip said:
> 
> 
> 
> 
> 
> Eric The Viking":1p2hjcip said:
> 
> 
> 
> For example, using an M8 bolt gives you 1mm per revolution (on a standard-pitch metric thread), or M10 does 1.5mm. I used my T11's through-table height adjuster to do this (M10 pitch).
> 
> 
> 
> 
> Being pedantic here, M8 has a pitch of 1.25mm. M6 has a pitch of 1mm :wink:
> 
> Click to expand...
> 
> 
> Also being pedantic, Common M8 pitches are 1.25mm or 1.5mm (fine or course)
> 
> Gerry
Click to expand...


Interesting :? I can't see, without a diagram or physical representation, how an M8 can have two different pitches. My understanding, which now falls into question  , was that M8, for example, was a specific diameter AND pitch. I haven't work with metal for a good many years, so maybe I'm missing something fundamental here. Apologies if something is very obvious, which I'm overlooking. Anyway, I CAN see two different pitches on the same diameter bolt; it's just that I can't for what I thought was a 'fixed' or 'standard' size M8.

Thanks for this information.


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## RWoody

ss03947":1rnrd5w7 said:


> do you know of any metalworkers in your area? (Probably not else you would already have tried them) Perhaps a look on a metalwork forum might bring up a new acquaintance? Doing the bulk of the work on a milling machine and finishing off by hand filing sounds the best and safest way to me.
> 
> 
> 
> 
> Woody, what's quoted in the post above, there's got to be a small workshop near by.
> 
> I've seen many an accident with milling machines never mind a router.. :shock: ..vibration is your worst enemy.
> 
> SS.
Click to expand...


Sure, ss03947, this is why I've come to this forum, as sometimes danger is closer than one thinks  Thanks for the warning anyway.


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## RWoody

wizard":x2yj7p4s said:


> just buy a milling machine, simples.



That's all well and good, but the point of this whole exercise is _not_ to buy yet another machine! If I can use or adapt my existing machinery, then so much the better, not to mention extra cost - especially as I'm unlikely to need to mill again like this. If I do, and it's ongoing for any reason, then of course I'd consider another machine, when space and funds permit.


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## Gerry

> Interesting :? I can't see, without a diagram or physical representation, how an M8 can have two different pitches. My understanding, which now falls into question  , was that M8, for example, was a specific diameter AND pitch. I haven't work with metal for a good many years, so maybe I'm missing something fundamental here. Apologies if something is very obvious, which I'm overlooking. Anyway, I CAN see two different pitches on the same diameter bolt; it's just that I can't for what I thought was a 'fixed' or 'standard' size M8.
> 
> Thanks for this information.



There are a variety of pitch/Diameter combinations in Metric screw threads. It's part of my job to measure and calibrate screw plug gauges to BS3643-2-2007

http://en.wikipedia.org/wiki/ISO_metric_screw_thread

Gerry


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## Eric The Viking

I was originally referring to the common sizes (and forgetting which was which!). 

It's easy to find out what you have, with bolt and a decent ruler: count eleven ridges along the bolt, and measure the distance. Do twenty if it's a small bolt!

Most of the commonly available stuff is metric 'coarse' pitch. As Gerry says, there's usually a fine pitch defined, too, especially for the larger sizes. They're rarely seen in DIY/construction, but I've come across them in the motor industry, for example the M10* bolts securing seatbelt webbing straps in our old Passat were fine pitch. The reasons are obvious - extra strength and less likelihood of unwinding by itself.

Similarly, there are uncommon metric bolt sizes. For example M7 is defined but hardly ever used in everyday applications, and I was amazed to find it was used for the battery clamp bolt on daughter's Rover 200. I now own three M7 bolts (always have spares!), which weren't cheap and had to be sought out locally, but I replaced the fitting with M8 (which everyone else uses) at the first opportunity. 

People used to grumble about the range of non-metric threads, but they all had a purpose. Some were easily done up/undone (Whit.), some had strength (BA, UNC, UNF) - you could use the right thread for the task. In a metric world one size fits all, unless you're in manufacturing.

E.

*might have been M12 - it was a long time ago. I still have the bolts somewhere...


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## RWoody

Gerry":54cbjy6r said:


> Interesting :? I can't see, without a diagram or physical representation, how an M8 can have two different pitches. My understanding, which now falls into question  , was that M8, for example, was a specific diameter AND pitch. I haven't work with metal for a good many years, so maybe I'm missing something fundamental here. Apologies if something is very obvious, which I'm overlooking. Anyway, I CAN see two different pitches on the same diameter bolt; it's just that I can't for what I thought was a 'fixed' or 'standard' size M8.
> 
> Thanks for this information.
> 
> 
> 
> 
> There are a variety of pitch/Diameter combinations in Metric screw threads. It's part of my job to measure and calibrate screw plug gauges to BS3643-2-2007
> 
> http://en.wikipedia.org/wiki/ISO_metric_screw_thread
> 
> Gerry
Click to expand...



Yes I can see it's pretty technical/complicated, though I understand what's being said, just - having just read the wikipedia definition. Thanks. 

I think I was struggling to get my head around the height vs pitch ratio; in as much as for the _same_ ratio, if the depth of thread was the same for one 8mm bolt compared to another, then of course the pitch would then _have_ to be the same. I'm not sure I'm explaining that very well, but I hope you get the gist. 

Anyway, all interesting to me, as is anything technical really. Thanks for your input.


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## RWoody

Eric The Viking":3hhdd2yh said:


> I was originally referring to the common sizes (and forgetting which was which!).
> 
> It's easy to find out what you have, with bolt and a decent ruler: count eleven ridges along the bolt, and measure the distance. Do twenty if it's a small bolt!
> 
> Most of the commonly available stuff is metric 'coarse' pitch. As Gerry says, there's usually a fine pitch defined, too, especially for the larger sizes. They're rarely seen in DIY/construction, but I've come across them in the motor industry, for example the M10* bolts securing seatbelt webbing straps in our old Passat were fine pitch. The reasons are obvious - extra strength and less likelihood of unwinding by itself.
> 
> Similarly, there are uncommon metric bolt sizes. For example M7 is defined but hardly ever used in everyday applications, and I was amazed to find it was used for the battery clamp bolt on daughter's Rover 200. I now own three M7 bolts (always have spares!), which weren't cheap and had to be sought out locally, but I replaced the fitting with M8 (which everyone else uses) at the first opportunity.
> 
> People used to grumble about the range of non-metric threads, but they all had a purpose. Some were easily done up/undone (Whit.), some had strength (BA, UNC, UNF) - you could use the right thread for the task. In a metric world one size fits all, unless you're in manufacturing.
> 
> E.
> 
> *might have been M12 - it was a long time ago. I still have the bolts somewhere...



Yes, Eric, I can see why specialists would prefer non-standard bolts for specific applications, as they're simply more suited to the job; and as you say, fine pitches indeed do have less tendency to work loose, for bolts used in situations where vibration is present. The shallower (meaning 'steeper' in this case) angle of the thread to the shank, has less tendency to slip, and hence work loose. One can also tighten to a greater compression force, for the same leverage (Nm poundage); though also making it easier to strip the threads, especially as the threads themselves would be thinner, so have less material within them. Interesting.

Thanks to you too.


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## seaco

I have used a straight and round over router cutters 1/2" to cut aluminium it cut really well I was surprised how easy it was, I was making a jig for my router out of 8mm thick ally and needed to make a recess in the middle for the router base so I just plunge cut it about 1mm at a time then I used the round over around the outside to make it look more professional...


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## RWoody

Thanks for your message, Lee. I can see that in your situation you'd have been less limited, by virtue of the fact that as you point out, you milled with a plunge action. Vibration and lateral cutting issues wouldn't have therefore have caused much difficulty. The potential problem I had, was one of long, lateral cuts, where the router, or workpiece, would me moving across the face of the cutters. 

I've decided what I'm going to do (having been busy on another job for a customer) and that is to 'file' the piece of brass I have which is so very near to fitting already, as suggested on this forum.

The other, much smaller, guide rail I shall purchase something made of a plastic-like substance. I have to look into this, and choose something easier to work with that also gives good longevity, so not prone to wear too quickly.

Then I shall purchase an Incra mitre gauge, and fit rivet-like pegs to the rail, which will slot into both the brass rail and the 'plastic' one. Having the 'pins' set/fixed immovably in the mitre gauge means that the gauge itself will remain in tact and square, as the wear will take place on the parts I've had to make up; so when things work loose eventually, I can replace the home-made parts without affecting the mitre gauge. Doing it this way would be preferable to having the holes drilled into the mitre gauge, and the pegs in the replacement parts, as when things work loose, it'd be the holes in the Incra mitre gauge itself. I really don't want to have to make, adjust or otherwise play around with that if I can avoid it. I'm not sure I've explained this very well; but I hope you understand what I'm getting at?

A big thank-you to everyone who has contributed. This is now hopefully solved. If it works really well, then I might photograph what I've done, if anyone would be interested to see? However, it it's only mediocre, then I won't feel like broadcasting it around as much.

All the best.

Ian


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## seaco

Glad your sorting it out pics are always welcome...


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