Drawbar M16 to 3/8 Adapter HELP.

Hi, Newby and made by first big mistake..!!!!

I have got myslef a 2nd hand Beaver mk2 Mill and is my first every machine/mill. The chuck needed for this mill is a INT40 and the only ones i could find had a M16 threaded drawbar. So, to go with my purchase of my new INT40 ER40 Chuck i got a lenght of M16 threaded bar to test it out. BUT..!!!!! the quill sharft is only 14mm wide.

So, does anyone know if you can buy an adapter that can use a 3/8 Darbar and thread onto a M16 chuck?

Or..... my Plan B, can anyone make the attached adapter for me? Happy to pay the cost of material, time and postage.

Any help and advice would be much welcome.

If you use what you have drawn to solve the problem, be very, very sure that the 3/8" drawbar will unscrew before the M16 thread.

If you are not very, very sure, put a double locking nut at the top of the 3/8" drawbar so you can drop everything out of the bottom of the spindle if necessary.

Have you checked there is enough headroom up inside the spindle taper to accommodate the 15mm height of 25mm diameter above the end of the 40 taper tool?

The M16 to M12 or M10 version of this might be a better solution:

https://www.ebay.co.uk/itm/325124381095

Loctite it into each tool and the drawbar will always come out as it should.

Could you not screw the 16mm allthread into the chuck, cut it off flush and drill and tap it to 3/8” to take the drawbar. Kind of like a threaded insert, fairly certain i did a similar thing when i had a 40 int Beaver. You could thread lock it into place.

Sorry, just read post above, which is an off the shelf solution of what i’m describing.

Edited By Alan Waddington 2 on 02/08/2023 22:16:53

At this point in the drama, his Uncle Murphy steps forward to inform us that the only drill chuck he owns is on a 40 taper with M16 drawbar thread...

But sounds like uncle murphy (OP) has a lathe so could drill and tap first using the lathe.

If headroom to clear the 15mm head of teh adaptor is an issue make a fluch one like Alan suggests but cut a slot in the end so it can be screwed in and you also have the option to screw it out again if needed.

My standard drawbar is 3/8 BSW, so a more modern arbor with a M12 thread is converted by screwing in, hard and and "Loctiting" a piece of M12 studding of the apprpriate length.

This is then faced , drilled, and tapped 3/8 BSW.

With a M14 or M16 thread, this should be less fraught.

The difficulty will be holdingbthe INT arbor, in the lathe, but no doubt a suitable holdr could be manufactured.

Howard

Maybe I was reading his stated "my first ever machine/mill" too literally. I wonder, if he has a lathe, why he would be asking for someone else to make the item pictured?

It is an interesting exercise to list the minimum amount of stuff needed to bootstrap him out of this hole.

My B&Q starter for ten: M16 threaded something, hacksaw, vice, cordless drill, 5mm drill bit, M6 tap, M6 threaded rod, M6 penny washer, M6 nut, 10mm spanner. Make the first one with an M6 female thread, the small diameter giving lots of wiggle room in the end of the M16 rod. Even if drilled not in the centre and not completely square it will still work. Use the first one to hold the ER chuck in the mill to make a second, much better one.

Who is next for machining 'name that tune'?

Hi All,

Thank you for the info and support... some great ideals. Would poss go with DC31k idea on the insert thread and change out to a M12 Drawdar to get me going. Then when up and running with some practice try and make the part at home.

Thanks again all....

I had the same problem, so I made a second draw-bar from various bits of scrap for my Myford VMB.

ISO40 tooling does not use a drawbar as such like MT or R8 so it will be difficult to change the design if the hole in the spindle is smaller than 16mm. The 3/8 drawbar will be marginal in strength for an industrial size fitting. I wonder if any adaptors to change from ISO 40 to ISO 30 could be used with a 12mm thread in the tooling. Maybe a 16mm ended drawbar turned down to fit through the spindle and assembled from the front would be ok for home shop use using decent high tensile steel.

Edited By old mart on 04/08/2023 18:40:22

You are the only person in this thread thus far to write ISO40. I think you are mistaken in that statement.

There are 40 taper specifications that are designed for use in an automatic tool changer, but the top of the tool is in every case threaded because the pull stud that one machine manufacturer uses is not the same as the pull stud that another manufacturer uses. Hence, for home workshop use, almost every type of 40 taper tooling can be used with a drawbar.

Sometimes if the tooling does not have the parallel shank at the top of it, a longer drawbar would be needed. Sometimes the tooling does not have the cut out for the drive dogs at the bottom of it, but it can be adapted.

I would question the assertion that the 3/8" drawbar would be marginal in strength. To give it some teeth, it would be necessary to calculate the tension that, let us say, a piece of M10 or 3/8" grade 4.8 studding will withstand and then come up with a plausible machining situation where that number might be approached closer than 50%.

We were taught to take a heavy mallet to then drawbar, for the INT 40 and 50 tapers, to break the taper, once the large drawbar had been slackened on the Cincinatti, Herbert and Thiel milling machines at Sentinel.

The facemills on verticals were retained by a large setscrew passing through the tool into the INT fitting. On the horizontals,the arbor was retained in the INT fitting by a drawbar.

Howard

Edited By Howard Lewis on 04/08/2023 20:30:25

Drawbars are essential for INT40 holders. The taper is self releasing (in theory) and so needs a positive means of retention. Drive is via dogs, not via friction on the tapered surfaces. The drawbar is simply to keep the holder in place, so strength is not an issue. All my INT40 tooling has a threaded parallel end; 5/8" BSW for older holders and M16 for newer holders. I think INT30 used 1/2" BSW.

As I understand it the Beaver mill came with INT30 as standard with an option for INT40. It seems strange that the quill bore is only 14mm. Either Beaver used custom INT40 holders to force the customer to buy from them. Or the conversion to INT40 isn't an original factory fit.

Andrew

I had assumed that the OP was talking about ISO 40 because of the mentioned 16mm thread wheras BT40 use 5/8". either way, the thread seems rather coarse to be used directly with a drawbar and not a pull stud.