# Which router cutter for stair strings.



## tomba26 (8 Oct 2010)

I have a set of stairs to make for a customer and she wants oak strings but mdf treads and plywood risers as it's going to be carpeted.
In the past I have used jigs that I knocked up in the shop but recently purchased a Unika stair jig. It suggests using a 16mm or 22mm dovetail cutter for routing the strings....I've never used a dovetail cutter before for this, only straights. Anyone used them before....any pros/cons or should I just stick a straight cutter in and be done?
Any problems with the dovetail tapering smaller and the strings being hardwood (oak)?
Thanks.


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## JoinerySolutions (9 Oct 2010)

The idea behind useing a dovetail cutter is so that when wedged up the treads and risers crush the strings wood fibres thus making a gap free joint between said treads/riseres and string.

For MDF treads I would not use less than 25mm thickness. 
Check out the Trend catalogue for their stair housing bit, and their instructions download for the way to set up/depth of housing etc.

An accurately made jig and a straight bit will do the job just as well, after all they never dovetailed the housings in the days when all was hand cut.
This stair I made last week, 25mm mdf treads 9mm ply risers and softwood strings, using mdf jig and 1/2" straight cutter.






















Rob.


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## tomba26 (9 Oct 2010)

Thanks Rob, I need some new cutters so I'll try some of the 16mm dovetails then. Looks like 16mm will work with my jig for up to 25mm mdf, then it's the bigger (more expensive no doubt) 22mm.

Stairs look good.  
Do you always use 9mm ply for the risers (for carpeted/covered stairs) or do you also use 12.5mm?


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## JonnyD (9 Oct 2010)

I used to use expensive cutters but moved on to these http://www.axminster.co.uk/axcaliber-do ... rod808970/ They seem to last as long as an expensive one and are really cheap.

cheers

jon


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## JoinerySolutions (9 Oct 2010)

tomba26":7adfjq88 said:


> Thanks Rob, I need some new cutters so I'll try some of the 16mm dovetails then. Looks like 16mm will work with my jig for up to 25mm mdf, then it's the bigger (more expensive no doubt) 22mm.
> 
> Stairs look good.
> Do you always use 9mm ply for the risers (for carpeted/covered stairs) or do you also use 12.5mm?



Depends on what gets specified by the architect. I have used 12mm or 1/2" ply and 9mm and 12mm mdf. Sometimes its all solid timber then its 18mm risers (no point in planing more of a 1" sawn board than neccessary)

Keep in mind when using the dovetailed cutters that they must be plunged fully to required depth *before* starting your cut and to let the cutter stop spinning before removing from the string or newel otherwise a gouge out of the top face will occur.
My Trend stair jig is over 20yrs old, but I rarely use it due to the sub base not fitting my latest router, I really should get off my backside and make a sub base to fit!
It also bears a scar when I got in a rush and dovetailed a slot out of it, two pack woodfiller fixed that.


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## tomba26 (9 Oct 2010)

JoinerySolutions":rpld4nac said:


> tomba26":rpld4nac said:
> 
> 
> > Keep in mind when using the dovetailed cutters that they must be plunged fully to required depth *before* starting your cut and to let the cutter stop spinning before removing from the string or newel otherwise a gouge out of the top face will occur.



That's the bit I'm a little worried about, the strings are solid oak and with a straight cutter I could do it in 2 or even 3 plunges if the cutter was struggling. I would think the dovetail cutter would struggle at full depth with one plunge and routering the strings?


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## JoinerySolutions (9 Oct 2010)

What size/make router are you using?


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## GazPal (9 Oct 2010)

tomba26":2mbt1fdj said:


> That's the bit I'm a little worried about, the strings are solid oak and with a straight cutter I could do it in 2 or even 3 plunges if the cutter was struggling. I would think the dovetail cutter would struggle at full depth with one plunge and routering the strings?



Route to full depth using a straight bit *before* dovetailing. Both bits should be bearing guided and capable of working to the same template. :wink:


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## tomba26 (9 Oct 2010)

Using a Makita 3612cx 1/2 router, 1850w power. I'm just dubious as to whether it will do full plunge routering on solid oak strings.


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## bench_monkey (10 Oct 2010)

in our shop we have always used trend 1/2" straights, im not too keen on the idea of dove tails, as long as its sharp a straight would give a flat edge for the tread/rise to sit on. it would also give me more confidence with wedging to, especially with the quality of oaks of late!


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## JoinerySolutions (10 Oct 2010)

tomba26":5sxffmz4 said:


> Using a Makita 3612cx 1/2 router, 1850w power. I'm just dubious as to whether it will do full plunge routering on solid oak strings.



Router is man enough. I made loads of stairs with the trend jig and their cutters using Elu177e routers.
I wore out the adjustable nosing piece of the sub base so had a new one made from Duralium :lol: 

Route the riser trench first and work around to the tread, check it is all done prior to moving the jig along, they are almost impossible to get located exactly where they came from.
On the strings start at the bottom of the string that would be on your left as you climb the stair and at the top end on the right hand string. 
This will reduce the risk of breakout at the corners where tread meets riser.

Rob.


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## tomba26 (10 Oct 2010)

Thanks for the reply Rob/Bench monkey. 
With regards the straight cutters, I have loads of 12.5mm kitchen worktop cutters, and I like the idea of using them as I found out yesterday the dovetails are not a stock item at either of my suppliers where I have accounts. I would have to order them and would be looking at wednesday realistically. Ideally I'd like to crack on mon/tues.
So....if I chose to use the 12.5mm straights, would this throw out the jig/sub base/bush combo or can I offset it in a way that would allow these to be used? 
It is the Unika stair jig if it helps.....here.....http://www.itslondon.co.uk/pd_UNISTAIRJ ... airJig.htm

Thanks again fellas, the info is very much appreciated.


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## bench_monkey (10 Oct 2010)

Now, we use one of those! You obviously got the pack with the router base and multiple guide bushes? ie - screw the base to the router and screw the guide bush to that base and follow the shape on the jig? that will be fine. As Rob also said, as long as you go left to right (and turn the jig over when you swap strings  ) it will be good enough. A new or sharp cutter is a must with oak however.

Currently have one of the chaps making two flights of solid oak (string/tread+rise) open ended stairs, wall side is a normal string, room side the tread/rise sits on blocks glued/screwed to a 6x3 s/w string with 1" oak glued to it, so you can imgine the fun we are having!!

Tom


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## JoinerySolutions (10 Oct 2010)

If in doubt do a test run on some scrap or mdf offcut, the critical point is the noseing over hang which needs to be a snug fit. Otherwise no worries just crack on and get that stair done, take some pics as you go for reference and to show future clients and post some here, we love pics. :lol: 

Tom sounds like a fun project you got on. These were good fun too!




















Have fun!
Rob.


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## katellwood (10 Oct 2010)

One issue i've always considered with dovetailed router bits for stair trenching is the glue surface, surely if the edge of the trench is tapered and the tread/riser square then the only direct glue contact is where the tread meets the outermost part of the trench, similar with the wedge on the underside. now i appreciate that in softwood strings there will be an element of compression to enhance the glueline however with oak strings this will not be the case.

In essence the wedge and the endgrain of the tread will be holding the stair together 

I use a 7/8 dia router cutter and use a separate jig for the tread and riser (this eliminates a 1/4 radius in the internal corner where the tread meets the riser) I then thickness my treads for a a tight fit for the nosing.

I route in two passes utilising the depth stop on my elu 177e 

My last staircase


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## JoinerySolutions (10 Oct 2010)

Nice stair Katellwood. \/ 

With the Trend sub-base system the gap is not produced, it occurrs when using guide bushes but can be resolved by using a pair of inserts to assist in letting the guide bush make a smooth straight run, no need for two jigs.
While I understand your concern re: dovetailed shoulders in tough woods like oak it really does not pose a problem. In the workshop pics posted above those stairs are dry assembled with lightly wedged treads and risers and one or two screws on the cut string side, no glue! I walked up them as I was assembling them, no issues.
What really holds these stairs together is the wedges, in all honesty there is little need to apply glue to the trenching, the bond strength between tread and riser and the trenched string is minimal, the main bond strength comes from glueing the wedges, it is a much larger surface area.
The frictional bond from a well wedged up tread or riser is extremely secure as you would know from trying to disassemble a stair over enthusiastically wedged up by an apprentice, many stairs I have made have to go to site as "flat packs" to get them in the building. :lol: 

So while square edged trenchings are absolutely fine so are dovetailed ones, the bits are not a 1:6 or 1:7 or 1:8 as per a drawer dovetail but a more shear 95/5° (1:6 being 171/9°) depending on where you measure the angle. So on a housing depth of 12mm as suggested by most literature, the gap between the tread and widest point of the dovetailed trench would be 1.05 mm before wedging up and most modern glues would be "gap filling" enough for that if we were really that concerned about it. Anyway thats all a bit technical and put people to sleep so what ever works for you...do. But enjoy it, else it's not worth doing. :wink: 
Rob, now going for a Sunday beer! :lol:


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## katellwood (10 Oct 2010)

Thanks for the comments Rob 

I think the most important issue on any solid string stair is to get the taper of the wedge exactly right


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## JoinerySolutions (10 Oct 2010)

katellwood":37wvaqcl said:


> Thanks for the comments Rob
> 
> I think the most important issue on any solid string stair is to get the taper of the wedge exactly right



Absolutely! They don't last as long as some I've taken out otherwise. :lol: :lol: 

All jokes aside, the interwebby thing chucks up a lot of poor advice, so we need to keep to facts and try to lose some of the misconceptions that we all, at some point, take on board as fact. Wickipeadia is a prime source by the way. 
On another forum I wrote about mortice and tenon joints, due to a number of mis-informed posts on the subject and an ex-pat brit quoted Wicki basically calling me a liar! Is he a professional woodworker? No! But believes what he reads first to be gospel. Well, hell the world is definately flat then! :lol: 
I loved my Elu routers and was saddened when one 'died' and later the other broke making the newel caps in the pics above. Glad to hear yours are still going strong, great tools.


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## tomba26 (10 Oct 2010)

Fantastic advise folks and some stunning staircases.  
Thanks again and I'll post pics when I'm done.


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## tomba26 (10 Oct 2010)

Bench Monkey am I correct in thinking there must be an adjustment made with either the jig/base combo or when marking out the strings if I use a 12.5mm straight cutter? The suggested cutter is 16mm dovetail and I am wanting to use a 12.5mm straight....this gives a 3.5mm difference?


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## bench_monkey (11 Oct 2010)

not really, the best thing to do is try a test piece first to get yourself familiar with the equipment. do you have 2 or 3 different guide bushes with the kit? it will be trial and error to get the correct setup for your job, we are set with a routine for all our flights now, 1/2" straight, 22mm treads, 1/2" risers. dont forget you can alter the size of wedge to suit the trench and board going in it. if memory serves, the centre point when marking out does not hit the middle point between tread/rise on the jig, as i say, trial and error. its the only way we learnt im afraid


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## tomba26 (11 Oct 2010)

Ok Tom, Thanks again.


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## bench_monkey (11 Oct 2010)

well heres our prize chimp and his masterpiece half way through. cack photo but our workshop isnt very photogenic!


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## chippy1970 (11 Oct 2010)

JoinerySolutions":2lfbzwlf said:


> The idea behind useing a dovetail cutter is so that when wedged up the treads and risers crush the strings wood fibres thus making a gap free joint between said treads/riseres and string.
> 
> For MDF treads I would not use less than 25mm thickness.
> Check out the Trend catalogue for their stair housing bit, and their instructions download for the way to set up/depth of housing etc.
> ...



Hi Rob I see youve picked up a few MUNGO systainers there, cheaper than buying Festool ones did you get them from bunnys bolts ??


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## JoinerySolutions (12 Oct 2010)

Yes Chris and it was all your fault! :lol: :lol: 
I caught one of your posts about them and ended up with three sys4 and a sys3. 
Sys 3 for router bits, two 4's for hand tools and one for various bits off the CMS kit.
Rob.


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## tomba26 (12 Oct 2010)

All, I used the new jig today and got it working in the end but initially had some problems getting the correct thickness of nosing to fit my treads.
The spec is oak strings and in the end they wanted 25mm mdf treads so I tried every combo of bush with the 12.5mm cutters I was going to use but just couldn't get near to 25mm which would let me have a snug fit for tread thickness at the nosing. It was either a few mm over or under the 25mm I wanted.
I knew for my 25mm treads the instructions said use a 16mm dovetail cutter and bush C, I didn't have any dovetails but found a couple of 16mm straight cutters so set the router up with that and everything else as suggested in the instructions. My nosing thickness/tread thickness ended up a little over the 25mm for a snug fit, it's much slacker than I would prefer, but after being glued and with the flight being carpeted it won't be seen.

I have a few questions though if you don't mind folks:

Any problem with the nosing being not as snug as I would like or is it mainly a cosmetic thing? I was going to use an expanding glue to soak up any slack (not that much) and the flight is to be carpeted so nothing will be seen.

Anyone else had problems getting a snug fit with 25mm mdf and 16mm or 12.5mm straight cutters?

Also why would the 16mm straight cutters still end up routering the treads a little oversize, would it be because the dovetails are 16mm at the widest point but as they are plunged into the timber you end up with less than the 16mm say?

For what it's worth I could have used 22mm mdf no problem as I found 
that eay to achieve with the 12.5mm cutters.

Sorry to ramble, so many questions, so little time.


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## tomba26 (12 Oct 2010)

edit:duplicate post sorry. Mods feel free to delete.


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## bench_monkey (12 Oct 2010)

yeah thats just like i said earlier, thats the set up we use tomba. must be the same jig then! 1\2" cutter, 22mm tread. have you tried it on a scrap or just gone for it?

the nosing is a mix of both in my eyes, obviously its nice to get a good fit for looks, but i think its good to have a good fit to hold the tread in a consistant place on each step. saying that, provided your rise is correct from tread to tread the gap can be made up somehow


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## JoinerySolutions (13 Oct 2010)

I think most purchased jigs are designed for 1" tread material which is 25.4mm so that could be the source of the problem if you have dead on 25mm mdf boards. Pva will take up the slack, stay away from polyurethane glues they are too messy around anything that will be clear finished.

Out of interest what is the width of the jig nosing aperture the bit that would determine the tred thickness?

Rob.


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## chippy1970 (19 Oct 2010)

JoinerySolutions":1rl2nw1z said:


> Yes Chris and it was all your fault! :lol: :lol:
> I caught one of your posts about them and ended up with three sys4 and a sys3.
> Sys 3 for router bits, two 4's for hand tools and one for various bits off the CMS kit.
> Rob.




:lol: :lol: :lol: glad to be of service :lol: 

they are pretty good value, i noticed the panasonic stand at the dm tool show were selling their ones but they were about £40 each.


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## scholar (19 Oct 2010)

JoinerySolutions and katellwood both posted some interesting pictures (thankyou).

I am interested in the curved handrails you have shown on the winder staircases - something I have in (slow) progress on a staircase I have at home. I have copied the curve of the stair string for the handrails and laminated some oak strips to that curve, so I now have a curved square section handrail; I am now wondering how to machine the required profile (could be on the router table or spindle moulder).

The top profile of the handrail should be relatively straightforward using a bearing guided roundover cutter and the sides of the workpiece flat on the table. I am thinking about how to machine the side profile, so some insight from JoinerySolutions and katellwood would be very much appreciated. (One possibility I am considering is to laminate the handrails in two parts so I can machine the profiles from both top and bottom and then join the two machined profiles - hope that makes sense - I have only laminated up one full depth piece so far and would have to remake that).

Any ideas would be gratefully received.

Cheers


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## JoinerySolutions (21 Oct 2010)

scholar":29snf4ld said:


> JoinerySolutions and katellwood both posted some interesting pictures (thankyou).
> 
> I am interested in the curved handrails you have shown on the winder staircases - something I have in (slow) progress on a staircase I have at home. I have copied the curve of the stair string for the handrails and laminated some oak strips to that curve, so I now have a curved square section handrail; I am now wondering how to machine the required profile (could be on the router table or spindle moulder).
> 
> ...



A lot depends on the profile and the rake or pitch that the curved part takes. On many 'one of' handrail wreaths I machine the straight runs and turn to a bandsaw and scratch stocks with plenty of hand sanding into the bargain, it is actually quicker than trying to go the machine route.
It is possible to make a laminated straight rail (not glued up) and then machine it and bend it to a former during glue up, still requires lots of sanding but is hard to describe but leaves either end in the correct plane to joint the straight runs.
You have probably concluded that the rail twists as it curves due to the pitch of the stair; think of a rectangular length of rubber and wrap it around a tube start at the bottom and wind it upwards, the rubber has to twist so the side of it remains flat against the tube. It is this that makes machining difficult or requiring many jigs. 
Much of the tooling that used to be in service for this kind of spindle work has been made illegal (with some good reasons) and now accomplished with CNC Router machines.
Post up some pics of what you want to do and a few more details (pitch/rise & going) etc and see what ideas come forward for your situation.

Rob.


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## katellwood (22 Oct 2010)

Hi 

As you can see my stair has two curved handrails one curved in plan the other in elevation, both were cut from the solid i.e. no laminating.

The one in plan was easy as the setup used to machine the straight sections was used with the aid of a ring fence on the spindle (the difficult bit was that the shape required was an ellipse as opposed to a radius).

The rail in elevation was slightly more difficult as the ring fence could not be used. The majority of the waste was removed with a router then meticulously shaped with scratch stocks and scrapers. The routing was carried out first then the rail attached to the straight section, this was joined with two 3/8 pieces of ply morticed into the underside then hidden with the balustrade groove. Following being joined to the straight section the shape was completed with scrapers and scratch stocks to the final finish 

One issue when utilising solid material in this way especially on the landing rail is that any tenons cut on the ends to attach to the newels are cut in extremely short grain therefore if draw bore dowels are used to pull up the joints there is a strong possibility of the tenon breaking. That being said if the joint is cut traditionally and the handrail section housed into the newel less force will be needed to pull up the shoulder as it will be hidden in the newel housing.

Hope this helps


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