R8 Drawbar Questions

[Kim]

As you may have seen in my other post, today was the first day I used my new Grizzly mill the way it was supposed to be used.  But I have a few questions about the R8 drawbar.

First question
How do you tighten it securely?

When I use my 3/4" wrench to tighten the drawbar down, the spindle moves.   There are some flats on the end of the quill that I could use to hold it steady, but they are wider than any wrench I own – its like 1 1/2" across flats or something.  (more than 1 1/4" for sure).


Do you NEED to use something to hold the quill end steady while you tighten?  Or is just snugging it up as best you can with the quill wiggling around good enough?

I used a pair of channel locks today, since that's all I had that would reach between those flats.  But I don't want to mark up the quill, so I think I need to find something better.  Do you guys use anything here?


Second question
I have been able to use several different R8 collets and holders in the mill, but when I went to try and use my new R8 drill chuck, it didn’t work.  I tightened the drawbar as far as it would go, but the chuck still wiggles up and down about 1/8”.  That doesn’t seem right.

So, I took the drawbar out and did some investigation with the R8 holders that would tighten up, comparing it to the R8 drill chuck that won’t, and here’s what I see.

It looks like the R8 Drill Chuck doesn’t let the draw bar screw in far enough to draw up tight – it bottoms out for some reason.  In most of the R8 holders the drawbar hole goes all the way through, even though it is only threaded part of the way.  So you can tighten the draw bar as far as is required.  But the Chuck only lets the drawbar go so far, then it bottoms-out.

Here’s a look at one of the working R8 holders with the drawbar screwed in as far as it will go.  Note that there is about 14.5” between the edge of the holder and bearing surface of the drawbar at the top.


And here’s the drill chuck screwed into the drawbar as far as it will go till it bottoms out.  You can see that 14.5” doesn’t get you to the same place on the R8 holder.


This is a close up – you can see there’s still 1/4” to 3/8” of threads to go, but the drawbar has bottomed out.


So, it seems I need to shorten my drawbar, or I need to figure out how to make the drawbar hole in the drill chuck deeper.  The second one seems hard, and I don't want to screw up the nice new keyless chuck, so I’m focusing on the first one.  My first thought was to make a 1/8” wide spacer, or use a stack of washers, to move the bearing face of the drawbar down some.

But looking at the top end of the drawbar, it looks like there’s a roll-pin holding the top in place so it won’t turn.  I was wondering if I could push that out and screw the hext nut on the drawbar another 1/8”or so.  Then I could make a new hold for the roll pin.


Do those sound like reasonable options?  Are there better ones?  Any other suggestions?

Thanks for the help!
Kim

PS Are R8 collets that variable?  Why don't they all fit without me having to make changes like this?  Seems like they would be standard or something...

[Jasonb]

The R8 SX2.7 I have on loan came with a pin spanner that fits the two holes in the end of the spindle



You could always place an 1/8" washer under the drawbar nut which will have the same effect as shortening the bar, I had to do that on one of my MT3 Drawbars.

[fumopuc]

Hi Kim, is it not possible to use a thick washer at the top under the hexagon, only If the R8 chuck collet  is in use ?

[Jo]

Hi Kim,

Drawbars - I have four for H and (currently) 2 for Tgs - threads and lengths are different. I also have a collection of spacers I have made to go under the top nut rather than have yet more different length draw bars 


As for tightening: an R8 collet needs a spanner on the bottom and top to pull it into the taper and tight with the tool. I am surprised the mill did not come with one. It is one of those mills that needs three hands when you are using collets - one for each spanner and the third for the tool  But you do gain head space 


I would suggest you make yourself a couple of dedicated length draw bars and try to use a short spanner nut on the end.  Maybe you could consider something which you can tighten the collet sufficiently by hand to hold the tool in place - both the BCA and Sexy have a knurled knobs which can be used to grip the tools before the finally tightening.

Jo

[Ramon Wilson]

Hi Kim,

I had a similar problem on my new mill 'cept it doesn't even have flats on the quill!

A simple solution for me and may be for you is to remove that long nut and make two nuts from it. One, with the cross hole still in, shorter than the other. Replace the longer nut on the draw bar and down the thread. Screw the shorter piece on until it is level with the end of the draw bar then drill through the cross hole and replace the dowel locking pin.

You can now pull up any tooling using two spanners of the same size, one on the fixed nut the other on the longer nut below. I have this system on both mills and it works just fine - you do not need to graunch tooling up too tight in the taper anyway.

Hope that helps - if you need me too I'll take a pic of them for you

Regards - Tug

[Ian S C]

My Rexon mill has a built in locking pin that engages a hole in the large pulley on the spindle. I have a number of draw bars, 10 mm, 3/8" ? UNC/BSW, and a 5/16" UNC for some homemade  #3 MT fittings. Where Kims machine has flats on the spindle nose, mine has a thread, onto which I screw my large diameter fly cutter, no draw bar needed.
Ian S C

[kvom]

My CNC mill uses a 36mm wrench to hold the spindle while I tighten the drawbar with a 12mm wrench.  I also have used washers or other spacers to shorten the drawbar when necessary.

[stevehuckss396]

My mill has a spindle brake handle. Looking at pictures of your mill on the interweb I saw a handle on the right side just under the motor. Is that a spindle brake?

[Doc]

 The draw bar if like the ones I've seen it the past do have a thick spacer. That is there so when or if your threads go bad at the collet end you cut it off and take the spacer out. They are made that way so you get a double use out of them.

[wagnmkr]

Just mill a wrench from flat bar stock. I made two of them that way and they work a treat.

Tom

[zeeprogrammer]

Regarding the spindle lock...this may not apply to you but may help some one else.
My mill also requires 3 hands and when using a collet I've had the cutter drop out as I loosened the drawbar.

I found this on the internet.

1st photo shows the drawbar.
2nd photo shows a stop I 3D printed. When loosening the drawbar, it prevents the spindle from turning.

Even though it was printed in a bright color to catch my attention...it's still easy to forget it's there when turning on the machine.
I'm going to attach something (like a bright red warning tag on a string) to it that either hangs down into the work area or over the start button.

[Kim]

Thank you everyone for the excellent and detailed answers.  I really appreciate it.

Sounds like it's common, if not expected, for R8 collets to require different lengths drawbars. And that a spacer solution is very workable.  I will probably go that route, rather than have multiple drawbars.

And I will fix me up a nice flat wrench to use in tightening the collets.

Again, I certainly appreciate all the help! Thank you!
Kim

[Lew Hartswick]

What?? You mean there isn't a spindle brake on that machine.  I can't imagine that (been using a Bridgeport for so many years). Sorry :-)
   ...lew...

[asm109]

My mill has no brake and no wrench flats on the spindle.
However, putting the spindle in back gear adds enough friction that I can tighten the drawbar without any spindle rotation.  YMMV.

[Stilldrillin]

When my R8 set arrived. Two of the collets had swarf, in the lower threads.

A 7/16 x 20 tap, soon cleared the way......

[Ramon Wilson]

Kim - I took these two pics earlier this morning 'just in case' - I think perhaps they are worth posting

Not wishing to labour a point but just in case you missed the significance of my previous post but this mod to the draw bar eliminates any need for spacers as the 'floating' nut takes care of any differences in draw bar length (within the limit of the thread length of course)
 

This is the draw bar made for the new mill - The top nut is held with one spanner the lower tightened to cinch up the tooling.



And this is the one fitted to the old Linley machine sometime in 1970. In fact I don't use a second spanner on the top nut on this machine just gripping across the belt to nip the pulley is sufficient to allow the tooling to be tightened. Neither drawbars have ever had to be removed.


A simple mod and one well worth investigating - or am I missing something here

Whatever, good luck with however you solve your problem and enjoy that new mill

Regards - Tug

[Kim]

Ahh... Thanks Tug!  Yes, the picture makes it very clear indeed!  I do like that idea.  You've made it into an adjustable length draw bar that way!

I may be investigating this method too!

Thanks for the great photos!
Kim

[Kim]

Well, I was going to put another nut on the upper threaded portion of my draw bar like Tug's picture, but I couldn't get the Hex end off.  I tried for a while then just gave up and made a 1/2" spacer.  And that works great.  I can now tighten up all my collets just fine!

Next I'll have to make a spanner for the quill (measured it and its 43mm) but that will come later.

Thanks!
Kim

[Ramon Wilson]

That's a pity Kim, guess they thread locked it or something as well as the roll pin 

Still you're now sorted - that's the main thing 

Tug

[Kim]

Yeah, I don't know what they did, but it just wouldn't budge.  And I didn't want to risk scaring up the pretty new draw bar by trying too hard to remove it.  So I just put the roll pin back in and did the spacer.

Thanks for all the help Tug & everyone!
Kim