3/8”/M10

Hi

Very simple and quick question…

The engineering suppliers in the UK do not realise that home machining is about as imperial as Jacob Rees-Mogg.

I want to buy a shell mill. ALL of the MT2 arbors I can find for sale have an M10 thread. My DW mill has a 3/8” drawbar and will not accept a M10 drawbar. I have read that they are so close as to be interchangeable. Is this correct, or is it a no-no for some reason?

(i.e. can I screw an M10 arbor onto a 3/8” drawbar?)

thanks

Steve

Edited By Steve355 on 17/09/2022 16:05:38

3/8" is 9.5mm so you are looking for 20thou. If you havn't got that to spare it's a tight hole. I have an imperial Centec 2B, I can get a 10mm drawbar in ! I used 10mm threaded rod, cheap, comes by the 1m. remember it is only to stop the arbor/ cutter falling out DO NOT DO IT VERY TIGHT ! Noel. Good Luck

If it's an insert shell mill you are looking at then it's more than likely to be 16, 22 or 27mm bore so the metric arbors these fit come with metric drawbar threads, If you find a 3/8W drawbar one it is more than likely to be 5/8 or 7/8 so won't be much use anyway

As M10 is reasonably coarse and the MT taper will do the griping consider making a drawbar from 3/8 round bar with an M10 thread cut on the end

Edited By JasonB on 17/09/2022 16:37:10

A 3/8" BSW will go about 4 threads into an M10 hole which is probably enough but I have run a 3/8" BSW tap into my M10 tooling and that then works fine with a 3/8" draw bar. As Noel says, a loose fit in the thread is OK for nipping up a 2MT.

Rod

I have converted M12 tappings in blank arbors to 3/8 BSW by Loctiting in a piece of M12 studding and then drill and tap to 3/8 BSW.

M10 (0.393" )is 8.5 mm ( 0.3362) Tapping size (Core dia 8.159 mm 0.321" ) 1.5 mm (p 0.059" ) pitch

3/8 BSW is 0.3125" Tapping Size, (Core diameter 0.295" ) 16 tpi (0.06252 ) pitch

The sizes and pitches seem all a little too close for plugging and retapping to be feasible.

My method would be to make up a drawbar with a M10 thread on the end, if that will pass through the spindle.

Howard

Try a length of 10mm studding down the spindle, it may fit without any modifications. When I converted the Tom Senior light vertical from MT2 to R8 it was easier to retain the top half of the spindle which had fine splines than to make one. The bore was intended for 3/8" Whitworth drawbars. I managed to get a 7/16" reamer through after silver soldering an extension to it. That is 11.11mm diameter.

Loctite in a short bit of M10 studding, drill and tap M6 and use M6 studding for drawbar. For MT tapers you don't need a strong pull, M6 plenty strong enough.

I can confirm that plugging and tapping won't work, having tried it myself. I made up an extra drawbar for the other thread in the end.

It would help if the exact bore size of the spindle was posted.

The Chinese vendors on eBay offer shell mill adapters wth either metric or Imperial threads.

I have two drawbars for my Amadeal mill. The milling R8 arbor is M10, the drill chuck and boring head are 3/8th BSW. I don't find it a problem, I just use the appropriate one.

More than 9.5mm and less than 10mm. I might just ream it to accept a 10mm thread.

————

TPI and pitch are different for those two threads? They are not compatible.

I have a DW mk1 mill that I made from the kit circa 1980. The spindle blank was supplied pre-drilled through at 11/32" for a 5/16" drawbar. Neither 3/8" nor M10 will fit. The tail of the spindle is 5/8" diameter with two opposed keyways cut into it 3/32" deep. There isn't enough metal left to drill it out for the larger drawbars. The OP might have the mk2 version of course and that might have a larger spindle - I can't help if so.

Andrew

If you can ream to 9.8mm and then use a length of 10mm studding with a long nut loctited to the top you would be good to go.