Author Topic: Drawbar hammer and drawbars  (Read 3757 times)

Offline Mayhem

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Drawbar hammer and drawbars
« on: October 06, 2015, 07:55:01 AM »
Been a while since I have posted here, so I thought I would share the drawbars that I made for my Kondia FV-1 mill as well as the hammer.

Given that I buy most of my tooling OS, I have ended up with two different threads on my tooling: 1/2-13 for the US stuff and M12x1.75 for the metric stuff.  Both are made from 4140, using ground and polished 1/2" pinned into 30mm stock that was turned and milled to for the hex.  The coloured grooves are so I don't mix them up!

The hammer uses a 1/2" drive 19mm socked and a weird brass pipe fitting that I found. It has a 1-14 threaded end and once screwed on, I filled it with lead.  I did contemplate simply knurling the handle but I decided to steel someones idea of making wooden scales.  The wood is recycled Jarrah (eucalyptus marginata) and I deliberately cut the wood looking for some imperfections.  Oiled with Ballistol and once that soaked in it got a polish with some locally made gun stock polish which leave a nice non-slip finish.

I'm really happy with these and they are much nicer to use than to two crappy ones I had been using (one came with the mill).  I also added a thrust washer which sits in the top of the housing and it works very well


Offline Arbalist

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Re: Drawbar hammer and drawbars
« Reply #1 on: October 06, 2015, 08:25:45 AM »
Nice job Mayhem. :thumbup: I've never had any problems knocking out the drawbar on my mill as I don't over tighten it but I used to get amused at our cousins over the pond bleating on about Morse tapers not being self ejecting in spite of the fact that on some machines they are. Mine wasn't though so I made one!



Bottom thread is M12 x 1.75 to fit all my tooling and the top is M14 x 1.25. I suppose it's a bit kinder on the mill but no big deal.

Offline Mayhem

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Re: Drawbar hammer and drawbars
« Reply #2 on: October 06, 2015, 09:12:20 AM »
Thanks Arbalist.  The NTMB30 taper doesn't require a beating but it does need a quick, firm tap to break free.  I've had one come loose once through inexperience and not wanting to over-tighten things.  With the thrust bearing, a quarter turn past the point of initial resistance has proved to be tight enough.

Offline Arbalist

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Re: Drawbar hammer and drawbars
« Reply #3 on: October 06, 2015, 09:57:42 AM »
On my MT3 tooling I just give it a sharp tap with a copper and hide hammer when required. Quite often though I have an MT3 ER32 chuck in the machine so it's a moot point anyway!

Offline Jonny

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Re: Drawbar hammer and drawbars
« Reply #4 on: October 06, 2015, 10:07:19 AM »
Used to have trouble knocking tapers out, use it often and wont have the problem.
I leave a 2Lb hammer by the side and 16mm spanner, spindle lock sharp tap and cutter out in 3 seconds, 7 secs later new cutter in grollied up. By this time still trying to undo ER with two hands.

Offline jcs0001

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Re: Drawbar hammer and drawbars
« Reply #5 on: October 06, 2015, 03:23:12 PM »
Good work - colour coding is a good idea.

John.

Offline mechman48

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Re: Drawbar hammer and drawbars
« Reply #6 on: October 07, 2015, 04:29:16 AM »
Very nice work. It is rare now for me to use a potential to kinetic energy converter on my WM16 mill as The self ejecting collar works well most of the time, once I feel the MT's pull together I tend to give it a 1/8 - 1/4 turn extra which I find is more than enough, not saying I haven't used the hammer, but very rare now.
George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'

Offline howsitwork?

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Re: Drawbar hammer and drawbars
« Reply #7 on: October 09, 2015, 06:01:59 PM »
very nice job.

Must say I still use a lead "adjuster" but only occasionally as made a captive draw bar, which (usually) works.

Like the idea of the thrust washer must give it a go when I use the 3/8 imperial draw bar on mine.

Offline JHovel

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Re: Drawbar hammer and drawbars
« Reply #8 on: October 10, 2015, 06:51:49 AM »
..... Mine wasn't though so I made one!

Bottom thread is M12 x 1.75 to fit all my tooling and the top is M14 x 1.25. I suppose it's a bit kinder on the mill but no big deal.

Hi Arbalist, can you help me understand your drawbar a bit better?
If I understand your concept, your threaded the other end of the spindle (or it was already threaded for the purpose) at a finer pitch than the tooling tapers? The ejection force is thus generated by the DIFFERENCE in pitch - unscrewing the tool fast than the drawbar fronm the spindle?
That seems very clever!
Could you have a loose nut to tighten the drawbar, independently from the length of the drawar? SOme of my MT4 tooling have a small variation in taper length and drawbar position. I manage that with various spacers and washers at present. But can't quite picture how it will work with an ejecting drawbar....

Cheers,
Joe
Cheers,
Joe

Offline Arbalist

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Re: Drawbar hammer and drawbars
« Reply #9 on: October 10, 2015, 07:19:58 AM »
Yes, it's just the difference in thread pitch Joe. I got the idea from Ralph, here:

http://modeleng.proboards.com/thread/5804/mill

Some of my tapers vary a bit in length but I've not had any problems with the operation of this draw bar. It works fine.