Captive Drawbar.

[Taf_PembsParticipant @taf_pembs]

Good evening all, better late than never.!

While I was doing the Chester write up a few people asked for some more detail on the captive drawbar I did for it.

I apologise it’s taken this long, I did forget then got side tracked and various other excuses etc etc.

Anyway, here are a couple of pics for the whole thing to save anyone hunting through the whole thread again for bits of it.

Firstly I found the drawbar itself inside a drive shaft from a VW beetle, I have quite a few as a mate gave me 7 or 8 from projects he had been doing (beach buggy things).

It’s 12mm, M12 threaded both ends with an integrated thrust bearing seat.

The thrust bearing set up on the shaft with a shouldered washer on top of it to locate with a suitably machined seat in the spindle.

This is looking through the slot in the spindle, with a collet holder inserted (the spindle taper is MT3) with the drawbar in the tightened position – thread drawbar into the tool holder until it seats then back it off ja thread or 2 to keep the drawbar loose so no restriction from it when pushing the tool holder into the taper.

I’ve circled the seat in the spindle where the thrust washer stack will land when extracting the tool holder.

This pic is with the drawbar being undone until the thrust bearing lands on the spindle seat prior to popping the tool holder out.

Here is a pic just showing the set up on a toolholder (ER32 collet holder in this case).

And, if you can cope with the ugly mug here is a short video of it in action. No spindle lock, just bottom gear on the head and a short sharp snatch on the tightening spanner I found to be more than enough tension on it, with a normal drawbar that took some clouting to remove! But as you’ll see removal is really easy and no hitting through bearings.

https://youtu.be/if5zBHSJc_M

 

I’m well happy with it as it’s easy enough to do left handed (with the right one still being knackered although getting some progress on that!).

Cheers all. 🍻

[DiogenesParticipant @diogenes]

👍..neat job – and good to know air-cooled VW’s aren’t a completely useless waste of metal after all 😂

[BazyleParticipant @bazyle]

Very interesting – and must have produced a lot of useful swarf. You rather glossed over the “suitably machined seat in the spindle”. Could you provide a bit more detail here please?

[not done it yetParticipant @notdoneityet]

Modern beetles were not air cooled.🙂

I have some peugeot drive shafts – they are not nice to machine.  Tried neither landrover nor morris minor ones. There is possibly a Mk1 cortina half shaft around somewhere…

That looked like a lot of metal removal, to find that drawbar!

[noel shelleyParticipant @noelshelley55608]

It’s good to see something made out of an unknown grade of steel – a neat job. All to often the advice is buy the right metal, this is fine if you have ample funds and can wait whilst it is delivered. For those on a shoestring budget or a tight time line it is worth trying to use what you have ? In this case the toughness of a halfshaft will be idea.

As For Diogenes comment, I like he also had a low opinion of beetles until a girlfriend had one and I HAD to work on it ! I could have the engine out in 20 mins and the only problem she had was a clutch – needed a new one = easy. It never had a coolant leak and the heater worked well. Noel.

[VicParticipant @vic]

Many years ago I came across an article by a German hobby machinist about a self ejecting drawbar for the common 626 milling machine like my Warco VMC. I used to be a member on another forum that had a lot of American members and one or two kept making derogatory remarks about Morse Tapers on milling machines not being self ejecting, so I made one. Not too difficult as luckily the top of the spindle will accommodate a M14 spark plug thread quite nicely and I happened to have a tap.

If anyone is interested the article is here:

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

[Taf_PembsParticipant @taf_pembs]

😂 The love hate of beetles!

The one in question is now powered by a 2L Supercharged (from a new type mini) air cooled boxer. Rear wheels are form an old ish 8 series BMW (his own that had nice aftermarket wheels) so are huge but have the advantage of stopping it wheelieing every time you give it the beans in 1st or 2nd!

As for the shaft, the centre drill in the webbed end was great for support as long as you mark the point where the web harness (just think diamond and your not far off) merges into the shaft (decent material) it is lovely to machine, leaves a great surface finish etc but traveling steady a must!

I have to admit to catching the webbed end of the shaft – not the web itself, just the shaft twice, which resulted in an immediately exploding WNMG insert 🙄🤦‍♂️ the only thing I could mark it with was a grinder.

I seem to remember there were a cup full of chips or 2.. it was free, I have several and it was decent material for repeated threading into hardened tool holders so seemed the perfect choice.

 

Bazyle,

I’ll have a hunt through the old pics and the original thread and find what I can re boring out the rough bit of spindle.

Essentially I set the compound angle to the same as I used for the washer tapered face and used a small boring bar with a ridiculous amount of stick out to take lots of really light cuts in the spindle bore so it was cleaned up enough for the thrust bearing assembly which was just removing lumps and bumps mostly apart from the last 2 or 3 mm which made it perfect to cut the seat with the compound to get a matched angle.

I tried to radius the outer corner (to match the washer) so as not leave any sharp internals and did manage just about, it’s not much as you can see but there is a radius there so happy enough. It was quite difficult as you can only see where you are through the slots as they come round – it was like working in a night club with a strobe going 😬😂

[Graham MeekParticipant @grahammeek88282]

Well done Taff,

It is nice to see an item being recycled and this being made into something useful for the workshop.

Regards

Gray,

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