Lathe mandrel clamp.

[olderdan]

When using my spring index indent http://www.homemadetools.net/forum/s...4049#post79248
I have noticed that while it is fine for drilling etc it does not provide enough rotational support for heavier milling operations so a means of clamping the spindle is needed, I decided to use my dividing attachment quadrant to keep work and materials to a minimum http://www.homemadetools.net/forum/m...5038#post81061
A scrap piece of aluminium plate was bored to fit a steel bush for the plain end of the mandrel, this bush has an interesting feature in that it is a press fit in the plate but a segment is split part way though the bush to provide clamping force by a screw. This method does not induce any rotational bias when clamped as a normal split clamp might do as it places the pressure though the centre line of a shaft, it it also does not harm the surface. A light hand tighten will securely lock a shaft and it is useful when there is not enough material to put a decent size brass pad under a bolt.
Used recently for milling a hex from round stock for some special cylinder head nuts.

[kquiggle]

Thanks for posting this - as it happens I have been looking for a good method to clamp a mandrel to prevent rotation, so your post came at an opportune time.

I wonder if it could be combined with a cam lever to provide for quick "on and off" clamping? If anyone else has good ideas along this line, I (and I am sure others) would appreciate hearing them.

[olderdan]

I wonder if it could be combined with a cam lever to provide for quick "on and off" clamping? If anyone else has good ideas along this line, I (and I am sure others) would appreciate hearing them.

Thanks for your comments.
I suppose a cam action would be possible but they are usually used for clamping parts together which is the opposite of the split bush design, I doubt it would be worth the extra work as a quarter turn with the finger screw is all that is needed to clamp enough for the flat belts on my lathe to slip off the pulleys when tested under power.

[kquiggle]

I agree that the "keep it simple" approach is a good one, and that is what I will do for my initial build.

The reason I asked about the cam action is that I am working on building an electronic dividing head (arduino powered) for cutting gears. For my initial build, I am not even going to include a spindle clamp, so I can see if the stepper motor has enough holding torque (probably not). However, I'm guessing that it is pretty likely that a spindle clamp will be needed, so I will make sure I can add one later. Similarly, although I will not initially build an automatic clamping mechanism, I want to make sure I can add one later if I want do, without having to do a complete re-build.

As for an automatic clamping mechanism, I was thinking of using a solenoid to activate the spindle clamp after each partial rotation. Right now I have all of the electronics (not including the solenoid) working, and I'm starting on the mandrel holding mechanism. Your posting came along at just the right time for me - previously I was searching the Internet for ideas, and coming up with nothing (searched on spindle lock, spindle clamp, mandrel lock, axle lock, shaft clamp, and numerous other variations and never came up with anything useful).

[DIYer]

Thanks olderdan! We've added your Lathe Mandrel Clamp to our Lathe Accessories category,
as well as to your builder page: olderdan's Homemade Tools. Your receipt:

Lathe Mandrel Clamp by olderdan

tags: lathe, clamp, mandrel

[olderdan]

Hi kquiggle
I see now why you are looking at an auto clamp system, I am using a manual lathe for milling odd shapes as well as symmetrical ones hence the need for a clamp, think of my chuck as a rotary table on a mill.
For milling gears I think you may not need a clamp as the cutting forces are axial, however if you do find it desirable I would think a reasonable sized solenoid acting on a plunger in place of the screw would be enough. I am outside my knowledge base here but I am sure others will be of more help.

[kquiggle]

I thought I would post a follow-up here about how I used the mandrel clamp idea in my electronic indexer build. I was not sure a rotation locking clamp would be needed, but in the end I am glad I included it because the holding torque of the stepper motor I used in not very high. For my version, I milled out the tab with a very small end-mill. As olderdan noted in previous comments, the amount of rotation required for a lock is not great (just over a quarter turn in my case), so I am just locking manually for now; I may look into some kind of solenoid operation later.

You can see pictures of my implementation on my indexer build page here:

https://sites.google.com/site/lagado...ing-head?pli=1

[Saltfever]

Edit . . .As for an automatic clamping mechanism, I was thinking of using a solenoid to activate the spindle clamp after each partial rotation. Right now I have all of the electronics (not including the solenoid) working, and I'm starting on the mandrel holding mechanism. Your posting came along at just the right time for me - previously I was searching the Internet for ideas, and coming up with nothing (searched on spindle lock, spindle clamp, mandrel lock, axle lock, shaft clamp, and numerous other variations and never came up with anything useful).

Tony Foale posted his clamp mechanism a while back. Search on Tony's name. IIRC, it was confined to the dimensions of his table. I'm very interested in your Dividing head idea. Hope you post here when done.

[Saltfever]

edit . . .A scrap piece of aluminium plate was bored to fit a steel bush for the plain end of the mandrel, this bush has an interesting feature in that it is a press fit in the plate but a segment is split part way though the bush to provide clamping force by a screw. This method does not induce any rotational bias when clamped as a normal split clamp might do as it places the pressure though the centre line of a shaft, it it also does not harm the surface.

Very interesting and unique idea! Many thanks for posting this.