(Mis)adventured in Morse taper turning (and a grinding question)

[sploo]

My lathe (a Colchester Chipmaster) has an unusual MT4.5 taper in the spindle nose. Apparently it would have come with an MT4.5 to MT3 adaptor, but they're rarer than rocking horse dung, and tend to be expensive when you can find one for sale.

I tried turning down a piece of mild steel with an external MT4.5 taper; which seemed to go ok. However, trying to then make the internal MT3 taper did not go well (way too much chatter with any boring bar I have that would fit).

So instead I turned to a short (~60mm) MT5 to MT3 adaptor I had. I put an MT3-to-25mm ground test bar in the 4 jaw, and got it dialled in pretty well (0.002mm TIR near the check, 0.006mm at the end; that's less than 1 ten thou to just over 2 ten thou for the imperial folks):

Existing adaptor mounted:

Turning went surprisingly well, and I hit the 1.5" (38.1mm) large end diameter (for MT4.5) pretty much perfectly:

Which turned out to be a mistake, as I should have probably left another 0.1mm on the diameter as it sits too deep in the bore. Regardless, it seats well and a check with some micrometer blue showed the contact with the spindle taper was decent:

Unfortunately, I still ended up with about 1 thou (0.025mm) of runout in the resulting MT3 taper, regardless of the orientation of the adaptor in the spindle. Ignore the reading on the dial, I was looking at the total swing:

I could have another go with a piece of mild steel, but does anyone have suggestions for how to bore a 60-80mm deep MT3 taper without getting chatter?

Alternatively, as the MT3 taper in the modified adaptor above could take maybe 0.1mm of material removal, I was wondering about trying to grind it in. Does anyone know the name of the tool arrowed below? It's a grinding stone on a long shaft, for a grinder (still taken from a YouTube video):

 

[deema]

I suspect the machine you’re looking for is a tool post grinder. Occasionally come up on auction sites but are silly price!
It needs rough turning, harden and tempering and then a final grind for accuracy.
Have you checked the bore of the lathe for any dings when stuff has been passed through. Just needs the slightest bruise for the centre to be out.

We’ve used a taper reamer to achieve an accurate bore after rough turning, but still doesn’t beat grinding.

 

[Katomi woodsmith]

Whilst watching an Axminster vid about live centres, they spoke of 4.5 mt
You could give them a shout, and see what they have

 

[Dr Al]

I made one of these for my lathe (a Harrison M250). I used a morse taper reamer for the final cut (after boring with a top-slide motor to minimise any wobbling from my cack-handedness with the hand wheels) and it seemed to work, with minimal run-out. Note that I cut the MT4.5 thread first and then did the internal bore with the adaptor fitted in the headstock, which probably helped keep that stage accurate.

However, I rarely use it to be honest. I'd originally made it with the intention of being able to hold Morse Taper tooling in the headstock, but there are surprisingly few times that I need to:

• I wanted a collet chuck, but rather than using an MT3 one, I made my own ER40 one with a MT4.5 taper on the outside. Given I was using home-made tooling, I figured I might as well minimise the chances of error by just having one piece involved (with MT4.5 and ER taper) rather than two (MT4.5 to MT3 and then MT3 to ER). I then found a source for a cheap-ish D1-3 spindle mounted ER40 chuck and that's so quick to fit / remove and has a bigger through bore so I rarely bother with the MT4.5 one.
• For turning between centres, I stick a bit of bar stock in the three-jaw chuck and turn the centre in place. The drive centre doesn't need to be hardened (as it's turning with the stock) and turning in place gives the ultimate in accuracy.
• My milling machine has an R8 spindle, so making tooling for that is never going to involve holding it in the lathe taper.

I'm sure there are other good reasons for morse taper mounting of stuff in the headstock, but I can't remember the last time one came up for me. I wonder if that's part of the reason that MT4.5 to MT3 adaptors are so rare: no-one ever used them so they ended up lost in a drawer somewhere.

 

[ChaiLatte]

It needs rough turning, harden and tempering and then a final grind for accuracy.

For one person pottering about in a workshop on a hobby basis, who will use the adaptor once a year for 20 minutes, what benefit does hardening and tempering achieve?

 

[deema]

If it’s soft, the slightest knock will cause it to no longer be true, equally unless everything is absolutely spotless it will scratch the surfaces creating lumps and bumps. You won’t be able to stone the dings off so you will be back to square one within a short time. Soft tooling is fine for say one or two uses only.

 

[Fergie 307]

For one person pottering about in a workshop on a hobby basis, who will use the adaptor once a year for 20 minutes, what benefit does hardening and tempering achieve?

I am guessing it would achieve more than your characteristically carmudgeonly contribution

 

[ChaiLatte]

I am guessing it would achieve more than your characteristically carmudgeonly contribution

Please address the issue raised.

It is very easy for someone to type 'harden and temper'; it is less easy for most people (especially the person needing the item) to carry that out.

Consider the practicalities of hardening and tempering the item. If a person did not have the facilities to do this in their workshop, what is the alternative? Send it out to be done commercially - and at what cost?

All I am saying is that with due consideration given to the context of the item's use, a serious cost/benefit analysis of the harden and temper option might reach a different conclusion to that above.

Would it be churlish to ask how many soft, blank Morse taper arbors are sold each year?

 

[sploo]

I suspect the machine you’re looking for is a tool post grinder. Occasionally come up on auction sites but are silly price!
It needs rough turning, harden and tempering and then a final grind for accuracy.
Have you checked the bore of the lathe for any dings when stuff has been passed through. Just needs the slightest bruise for the centre to be out.

We’ve used a taper reamer to achieve an accurate bore after rough turning, but still doesn’t beat grinding.

Understood on the existence of a tool post grinder (I've seen a few DIY versions over the years, and considered making one myself). I was wondering about the tool being held by the grinder (whether it's a small cylindrical stone held in long chuck/bar, or whether the stone and metal shaft come as one piece). At least from the video I saw I couldn't see a grub screw in the bar that might clamp the metal shaft of a cylindrical stone; so it wasn't clear how the stone fits to the grinder shaft.

I'm reasonably certain the bore on the lathe is good. Certainly when I was running the micrometer blue around the inside I couldn't feel any bumps.

Re a reamer; I understand that if the MT3 bore has runout then a reamer would follow the runout, or is it a case that a very careful application of a reamer would "fix" the runout? I suppose an MT3 reamer would have a reasonable diameter of material to keep it straight even under load.

Whilst watching an Axminster vid about live centres, they spoke of 4.5 mt
You could give them a shout, and see what they have

Couldn't see anything on their website unfortunately.

I made one of these for my lathe (a Harrison M250). I used a morse taper reamer for the final cut (after boring with a top-slide motor to minimise any wobbling from my cack-handedness with the hand wheels) and it seemed to work, with minimal run-out. Note that I cut the MT4.5 thread first and then did the internal bore with the adaptor fitted in the headstock, which probably helped keep that stage accurate.

However, I rarely use it to be honest. I'd originally made it with the intention of being able to hold Morse Taper tooling in the headstock, but there are surprisingly few times that I need to:

• I wanted a collet chuck, but rather than using an MT3 one, I made my own ER40 one with a MT4.5 taper on the outside. Given I was using home-made tooling, I figured I might as well minimise the chances of error by just having one piece involved (with MT4.5 and ER taper) rather than two (MT4.5 to MT3 and then MT3 to ER). I then found a source for a cheap-ish D1-3 spindle mounted ER40 chuck and that's so quick to fit / remove and has a bigger through bore so I rarely bother with the MT4.5 one.
• For turning between centres, I stick a bit of bar stock in the three-jaw chuck and turn the centre in place. The drive centre doesn't need to be hardened (as it's turning with the stock) and turning in place gives the ultimate in accuracy.
• My milling machine has an R8 spindle, so making tooling for that is never going to involve holding it in the lathe taper.

I'm sure there are other good reasons for morse taper mounting of stuff in the headstock, but I can't remember the last time one came up for me. I wonder if that's part of the reason that MT4.5 to MT3 adaptors are so rare: no-one ever used them so they ended up lost in a drawer somewhere.

Lots of good points there. It's somewhat of a "completionism" project; as it's something I've wanted ever since I got the lathe. Plus it's good practice turning accurate tapers (not something I've ever really needed to do before).

I have a few chucks, including an ER40 plate that I adapted with a D1-3 backplate, and yes, I've turned a point in some stock in the three-jaw when I've needed an accurate centre. So I guess I probably wouldn't use it much - just nice to have.

My mill does use MT3 though; and what's sparked this off is that I wanted to accurately (lathe) machine an MT3 tool for use in the mill. I may instead end up mounting a lathe cutter in the mill vice and using it as a vertical lathe.

For one person pottering about in a workshop on a hobby basis, who will use the adaptor once a year for 20 minutes, what benefit does hardening and tempering achieve?

It's a fair point. I have hardened and tempered smaller parts before. I'm not sure I'd be able to get something of the size/mass of an MT4.5 to MT3 adaptor up to be required temperature with a MAPP torch though. Obviously it would move a bit, then need grinding (which is also something I can't currently do - but would be interested to add).

 

[Fergie 307]

Another way would be to get a straight shank to MT adaptor, then centre the adaptor in a four jaw chuck. Gives you a MT fitting to the spindle, although obviously loses you some distance between centres.
There are two types available, a sleeve with a straight outer and a MT bore, or the type with a MT socket on the end of a straight shank. A potential solution, albeit not quite what you wanted.
RDG do the latter type in 3/4-MT3 for £14.50. Sleeve ones are rather more pricey.

 

[Tony Gold Coast]

Grizzly sells them
https://www.grizzly.com/parts/-spindle-sleeve-mt-4.5-mt-3/p97302912

 

[Fergie 307]

Grizzly sells them
https://www.grizzly.com/parts/-spindle-sleeve-mt-4.5-mt-3/p97302912

I don't think they will ship to the UK.
You might get someone on that side of the pond to buy it and ship it to you. I have done this before with members of other forums. Good price, how much she shipping would be I don't know.
Given that on the rare occasions they come up over here the price is often £90ish, it might still be good even with the shipping. Depends how much you want one.
I have one for my Harrison, don't use it that often but handy when you do need it.

 

[Amplidyne]

Why not ask the companies like RDG, Chronos etc. if they can get hold of them?
You often find with places that they can obtain special stuff, but don't stock or list it.

 

[sploo]

Another way would be to get a straight shank to MT adaptor, then centre the adaptor in a four jaw chuck. Gives you a MT fitting to the spindle, although obviously loses you some distance between centres.
There are two types available, a sleeve with a straight outer and a MT bore, or the type with a MT socket on the end of a straight shank. A potential solution, albeit not quite what you wanted.
RDG do the latter type in 3/4-MT3 for £14.50. Sleeve ones are rather more pricey.

That probably defeats the "ease of use" point of just being able to throw an MT3 tool into the lathe bore.

Grizzly sells them
https://www.grizzly.com/parts/-spindle-sleeve-mt-4.5-mt-3/p97302912

As Fergie noted; unfortunately they don't appear to ship to the UK, and US to UK shipping always seems to be quite expensive (plus all the taxes on top).

Why not ask the companies like RDG, Chronos etc. if they can get hold of them?
You often find with places that they can obtain special stuff, but don't stock or list it.

Worth a go I guess. I suspect most of the stuff they get is made in bulk in China, so unless there were an MT4.5-MT3 adaptor from a similar source then the problem would be the inevitable high cost.

On the Colchester and Harrison Yahoo forums there are occasionally people that get a batch made; which seems to be the most common (cost effective) method.

 

[Fergie 307]

I have had a number of items from US only sellers, bought for me and shipped by members on other forums. One guy on the Harrison lathe group has done this for me a number of times. One advantage is that you avoid paying the extra tax that I assume a commercial seller is obliged to charge an overseas customer? In any case it has always proved very reasonable cost wise.
Probably worth asking on the lathe user groups, you might find someone who has one they would be prepared to sell.
Or check on e bay USA site, not all sellers charge extra taxes, I assume it's something that varies from state to state? E bay global shipping or USPS are usually not outrageously expensive.

 

[Fergie 307]

This guy has the sleeves
https://www.ebay.co.uk/itm/40545341...WIuiM1R6-&var=&widget_ver=artemis&media=EMAIL

 

[sploo]

This guy has the sleeves
https://www.ebay.co.uk/itm/40545341...WIuiM1R6-&var=&widget_ver=artemis&media=EMAIL

Interesting. Says 1.5" OD but not that they're tapered. I've sent the seller a message.

 

[schnapps95]

Interesting. Says 1.5" OD but not that they're tapered. I've sent the seller a message.

I think he does he say's No's 1,2 & 3 morse tapers and looking at the photo's there is 1 No1, 1 No2 & 3 No 3