Slitting saw arbour

Hi,

I have a few 1" bore slitting saws but no arbour for my mill. I am thinking of making one and have a couple of questions.

Would a parallel shank in in ER collet work OK or would a MT be needed?

What diameter should the clamping part be? I was thinking 1 1/4" which would give 1/8" clamping. Or would 1 1/2" be better?

Would EN1a/EN3 be strong enough?

Thanks

Adrian

Here's two I made earlier, both EN1A with parallel shanks to fit ER32:

The clamping part on the 1" arbour is 30mm, slightly less than 1¼" and it grips OK.

Note the flats milled to allow the arbour to be held by an adjustable spanner for tightening and undoing the bolt.

Dave

Thanks for the picture Dave, that is exactly how I imagined making it.

Hi Arsath,

The tool is made to hold a slitting saw, which cut metal. I use them mainly to cut screwdriver slots in home-made machine screws.

Mostly mounted in the spindle of a milling machine, where it can be moved to cut a horizontal slot into work held in the vice:

Dave

Hi Dave, I like those arbours you made.

Are you relying on the clamping action to hold the saw in place or do you use a key way to engage in the saw?

I always feel that if the keyway is used than it will be goodbye saw if it gets stuck in a slot.. Instead if the two clamps are used to retain the saw as in your arbour, in the event of the saw gutting stuck then it "may" not be the end of the saw.

A bought a small slitting saw arbour, and it was rubbish, I will copy yours....if you don't mind !

Regards

Derek

Adrian

I made one very similar to Dave's many years ago but with a MT #2 taper to use in the lathe. I didn't put flats on it and tighten and untighten it up once mounted in the spindle which I found works OK. The clamping washer is 1 1/4' so only has 1/8" of clamping surface but holds the saw securely and if it does slip I consider it a safety feature. I now use it only in the vert. mil mounted in a #2 to R8 adapter, with the draw bar into the thread in the morse taper. If you use a morse taper ensure you use a draw bar as they tend to come loose if subjected to side pressure as in this case. I have used mine many times in all types of metal with saws from 1/32 up to 3/16" and have found it more than satisfactory

John

Clamping only because I share your concern about key-ways. So far no slipping - I don't do a lot of slitting though. Feel free to copy - I'd be amazed if the idea is original!

Dave

The arbour I made , has the 25.42mm bore, that is 10mm deep. It then has a M8 tap hole a further 16mm deep.

The cap has the 25.40mm spigot, 8mm long, and at the shoulder, it is continued in an under cut way for 0.3mm deep, just a little more than the tool radius. The shoulder face is under cut out to about a 3mm land. In my case the arbour shaft is 19mm and the body is Ø40mm. I made it with the spigot on the nut, as the nut could then be thinner on the underside, and has the capscrew counter bored in it. Longer caps can be made for a gang of saws if required. Make the cap from a different steel to the body, so that it is less likely to pick up in any way. Like 4340 for the body and free cutting MS for the Cap.

Neil

Edited By Neil Lickfold on 17/06/2019 20:26:16

My arbor is almost identical to Neil's above ( but with a #2MT shank), except that I made the cap spigot 1/2" long and the flange 3/16" thick. This allowed me to recess the 1/4" hex socket retaining screw fully into the cap which allows the unit to be used very close to the vice jaws or other surface.

John

Using a parallel shank in an ER collet, introduces two possible sources of error.

One: the concentricity of your shop made shank to the register for the saw, and

Two; any errors (angular or concentric ) in the ER collet system.

If you cut the register for the saw on a MT arbor, located in the MT socket in the lathe mandrel, it should be concentric.

Guess which method I use?

Howard

I guess it might be better to use a MT, I was thinking straight shank as I have not successfully made a MT before, plus the complication of creating the draw bar thread.

I guess cutting the draw bar thread first, then put a bolt in the hole and cut a centre in the bolt solves that problem.

If I screw up the MT I can still turn it down to a straight shank.

Adrian

You might like to peruse this thread **LINK** in relation to a keyed arbor or not. Howard describes the possible outcome quite succinctly!

Well, I made mine straight-shanked in an ordinary 3-jaw chuck. My soul revolts against unnecessary work and a slitting saw doesn't need careful centring does it?

That slitting disks often arrive brand-new with noticeable 'run-out' is being discussed in another thread at the moment. If the disks mounted in the tool are themselves slightly off, then I feel concentricity of the arbour need not be special beyond ordinary good-condition 3-jaw accuracy. Mine works fine despite being made to do the job with minimum effort.

Dave

Edited By SillyOldDuffer on 19/06/2019 08:28:36

Here is one I made 30 odd years ago, 3 MT with draw bar thread, no keyway, made from bright mild steel. Not sure if EN numbers for steel were invented back then, or at least I didn't know about them if they were!

Spanner flats or a tommy bar hole would be a good modification for me to make. I would suggest you make the end cap thin and flush fitting, as this allows you to work close to any obstacles on the part you are cutting, or close to the machine table/cross-slide etc. Not touched any engineering since the mid 1980's, just making a re-entry to to this hobby.

I do not kid myself that I can produce a 3 MT taper as accurately as the commercially made ones, in terms of accuracy or surface finish, so I buy a soft arbor and machine the register for the Slotting Saw.

Often, my problem is that my drawbar is 3/8 BSW and the arbor is M12. Being too idle to make a M12 drawbar, which is what i should do. I make and fit a bush with M12 external thread and 3/8 BSW internal. This leaves very little metal between the two threads, but has sufficed so far..

Lazy? Yes, but I prefer making the things that i want, rather than being frustrated trying to make a taper which is inferior to the ones I could buy

Howard

Hi Howard,

I’ve done the same. Fit a bar and then machine the shaft.

Do you shrink fit, solder or loctite the arbor into the soft-ended MT? Pinned as well?

I knocked up a 22mm arbor for my horizontal mill. I shrink-fitted it - but machining for a clearance, rather than an interference, fit would be easier, should I need another. I did not fit a cross-pin but I doubt it will ever shift as this arbor has only been used for gear cutting and slitting saws.

NDIY

The register is cut into the stub arbor. This ensures concentricity with the Morse Taper, keeping things short and rigid, The longer the arbor is the more likely it is to flex.under cutting loads

If you HAVE to extend the arbor, my method would be (assuming that the register is going to be 1 inch ).

1 ) Drill / ream the hole for the extension, in the MT arbor.

2 ) Turn the the mating diameter of the extension,

(MUST be made from metal which is bigger than inch diameter. )

3 ) Press / Loctite / clamp with a grubscrew, the extension onto the MT arbor.

4 ) Turn / drill / countersink the Clamping cap, which will clamp the Saw to the new arbor. The clearance over the register should only be just in excess of the 1 inch register.

5 ) Turn the 1 inch register for the Slitting Saw on the extension of the MT arbor

6  ) Drill / Tap for the Clamp Screw.

4 could probably be postponed until after 5 and 6.

You should then be able to assemble the completed Slitting Saw arbor with a suitable countersunk head capscrew, ready for use in anger.

Howard

Forgot to leave a space to avoid the confounded emoji!

Edited By Howard Lewis on 20/06/2019 17:44:15

Finally got round to making the arbour. Chose mix and match all the ideas posted to make a MT2 with plug type cap. Had to limit it to only holding up to a 1/8" blade as I only had a short counter sunk screw. I tried it out and it runs true and cuts perfectly.

Adrian

Looks good Adrian, best get a longer screw just to be sure.

Emgee