Making a Drawbar

[DellParticipant @dell]

Hi all

I want to make a drawbar for some 10mm Schaublin collets I have about 50 because they are a perfect fit for a Pultra , even the chap at Smart&Brown said that’s what they recommend because Pultra collets are so hard to find, I have a M10X.75 tap but I am not sure what to use to make the bar , will mild bright steel be strong enough, or would stainless steel be better, also if mild steel would be okay would I need to harden it,

thanks Dell

[DellParticipant @dell]

[Anonymous]

Low carbon steel will be fine. Casehardening would be icing on the cake, but isn't strictly necessary. When I made a drawbar for my horizontal mill I used EN16T, but only because I had the needed 16mm diameter in stock.

Andrew

[OldironParticipant @oldiron]

Mild steel should be more than adequate. Draw bars do not need to be tightened too much. Both my mills have mild steel draw bars in metric & imperial and never had a problem. None of them are hardened.

regards

[Thor 🇳🇴Participant @thor]

Hi Dell,

For the drawbars I have made I used mild steel (S355 mostly) and I didn't harden them. The oldest are over 10 years old and still work without problems. My drawbars use a coarser thread than M10 x 0.75. If mild steel wears too quickly you could just make a new one.

Thor

[Ady1Participant @ady1]

I use 6mm threaded rod on my Drummond mt collets which are hardened

The threaded rod is sacrificial although I've used it a lot and its still fine

The main thing is don't tighten the collets too much or they can get pretty tight

[DellParticipant @dell]

Thanks everyone I just checked my Pultra drawbar with a file and it’s not hard.

[Roderick JenkinsParticipant @roderickjenkins93242]

Bear in mind chaps that we are talking about a hollow drawbar here with an internal thread on relatively thin walled tube. I'm not close to my Pultra at the moment so can't measure the wall thickness or comment on the hardness of the Pultra supplied drawbar.

Rod

Edit: Dell , Out of interest, what is the diameter of the Pultra draw bar?

Edited By Roderick Jenkins on 07/04/2022 20:02:40

[mark costello 1Participant @markcostello1]

I used plain old mild steel for Mine. 1018 steel don't know what You call it over there. I added about 3 " to allow for one or two cut offs and rethreads if it wears out. Used about 5 years now with no problems.

[DellParticipant @dell]

Roderick

both my Pultra drawbars measure 11.45mm OD and the ID of the spindle is 12.4mm so a length of steel tube

12mm OD and 8 or 9mm ID should do without the need to turn OD down.

Dell

[Roderick JenkinsParticipant @roderickjenkins93242]

[Howard LewisParticipant @howardlewis46836]

There is no need to tighten the drawbar into yield..

Sufficient force can be generated by a M6 thread to fracture cast iron in the right circumstances.

Mild steel with M6 threads should be more than sufficient to close the collets to grip the workpiece.

Howard.

[JasonBModerator @jasonb]

Bit of this stuff for a drawtube would be worthy of the Schaublin, they do 12mm OD in several wall thicknesses

[DellParticipant @dell]

Thanks JasonB

that’s what I have got but I have since found out that the thread is M10 X .8 buttress and I can’t find a tap of that size, I don’t know if it’s possible for it to be done on a screw cutting lathe.

Dell

[Howard LewisParticipant @howardlewis46836]

If you can set up the lathe for a 0.8 mm pitch thread, a suitably ground tool should allow you to do the job.

Howard

[DellParticipant @dell]

Will have to go to my local engineering company to see if they can do it because my Pultra doesn’t have screw cutting.

Dell

[Roderick JenkinsParticipant @roderickjenkins93242]

Dell,

I have sent you a PM.

Rod

[DellParticipant @dell]

I just wanted to give a big shout out to the wonderful people on this forum especially Roderick Jenkins who has made me a couple of drawbars so I can use my many Schaublin 10mm collets in my Pultra 17/70 and won’t take a penny in payment so I am going to make a donation to charity, but not just Rod but also Clive steer who made a spindle shroud for me, Noel and many others, this is a wonderful forum and it has some very knowledgeable and helpful people long may it continue.

Dell

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