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Member postings for Pete Rimmer

Here is a list of all the postings Pete Rimmer has made in our forums. Click on a thread name to jump to the thread.

Thread: spindle thread
04/02/2021 16:58:41

I don't find it unusual at all. I had to make a backplate for a IXL dividing head last week which was 1-41/64" - 11tpi

Thread: Cutting a Worm Wheel
04/02/2021 12:55:52

What is the pitch of the worm Stephen?

Post some pic if you can.

Thread: Gear Hobbing computations assistance requested
02/02/2021 09:54:39

Oh I see what you mean now. Yes, ideally your cutter would be the same diameter as the worm for full contact, which would of course make the helix the same.

The only worm wheels I usually cut are thread chasing dial wheels which carry no load. I made one this week for a Smart & Brown lathe.

02/02/2021 09:16:48

Phil,

If you set the head vertical, you'll generate teeth on the wheel set at the helix angle of the hob. If the angle of the hob is different to the helix angle of the worm, you have to adjust for the difference.

Pete.

01/02/2021 22:16:51

For hobbing a worm wheel you have no choice but to feed directly in (unless using a dedicated hobber with a 4-gear or electronic setup so you can make a full depth bevel cut in one pass). My machine can cut spur gears conventionally or worm wheels straight-in. To do a worm wheel with the teeth set at the helix angle of the worm I set the head over by the helix angle and feed directly in.

01/02/2021 20:28:16

To combat back-lash you could take two discs and fix them together. Hob your worm on the centre line then mill a couple of slots in the walls of the discs but make one slightly longer. Put springs in the pockets so that they try to rotate them relative to each other. That way both flanks of the worm will be loaded at all times regardless of the direction of rotation.

Thread: Jacobs Chuck
01/02/2021 16:58:08

The outer ring is a press fit on the screw ring inside. Seems like yours is slipping. Check the outer ring carefully for any hair-line cracks especially in the bottom corner of the grooves.

Thread: Eagle Surface grinder - who here uses one?
01/02/2021 13:45:28
Posted by James Burden on 31/01/2021 20:08:04:

Also Pete - meant to say, have read your thread on the mig welding forum start to finish, really impressive stuff.

Thanks you!

Yes you're right my housing has a step to seat the outer races against at the back. The spindle also has a step for the inner races. The outer races are clamped by the nose piece at the front and the inner races by the wheel hub.

Thread: Gear Hobbing computations assistance requested
01/02/2021 13:37:57

All that happens is that the profile of each tooth is slightly different. If you go bigger on th e OD you get more tooth and less gap, smaller you get less tooth and more gap. This is why gears are specified at PCD - the tooth and gap are equal there.

If fairness, because you have the facility the best thing to do is what you say - adjust the OD/PCD to suit your cutter's pitch. Then you don't have to worry about it.

01/02/2021 11:41:41

That's the point you will not erode all of the teeth because you're not relying on spacing but on indexing. The 4mm error is spread between the teeth but it's not added together to leave a gap at the end. On the first turn you have 158 indexes, on the second turn you have 158 indexes, and so-on. After ten turns you'll still have 158 indexes and each one will be in the exact same place as all the other turns.

This is how profile-shifting is used to reduce under-cut on low tooth-count gears. You increase the diameter to change the tooth form.

EDIT: John beat me to it.

Edited By Pete Rimmer on 01/02/2021 11:43:08

01/02/2021 10:10:22

Posted by Joseph Noci 1 on 01/02/2021 05:51:47:

Pete, if I extrapolate your 1 thou error, for a 158 tooth gear, it give a 4mm 'error; after once around the blank, so I would need to increase the blank diameter or reduce the number of teeth - the latter being no problem. The problem being obtaining said hob - complicated from where I live here in Namibia.. The forces and torque involved in the application are very low, speeds are very low indeed - the wheel max rpm is typically 1rpm, so the worm runs around 150 to 200rpm max. and accelerations are gentle.

Joe

With small errors you'll get a slight deviation in tooth form but you will always get the number of teeth you asked for and they will always be evenly spaced when hobbing (or dividing, so long as you don't mess up in your indexing).

31/01/2021 20:17:09

Joe if you get a 35dp hob it will come very close indeed to your 90 thou pitch (It's one thou per pitch different). Then you can turn a proper acme screw to drive it.

What are you doing about removing backlash?

Thread: Mounting a Mitutoyo dial gauge
31/01/2021 12:31:08

Put the mag mount on the sliding strip with the gauge down low next to the base. Angle the tip down if you like - it will over-read somewhat but it will yell you where the problem lies.

Another thing you could do is make a plain back and swap it out temporarily, Usually, they are just disc of plain metal.

Thread: Eagle Surface grinder - who here uses one?
31/01/2021 10:08:43
Posted by James Burden on 30/01/2021 23:00:04:

Hi Pete,

Just found this thread and read with interest. I must say, you have made a lovely job of your grinder, really nice. I picked up a Mk3 Eagle grinder a few years ago, overall in good condition without excessive wear. I rebuilt the base and knee, ways looked OK, made new leadscrew and nut for the Y feed, but I didn't get any further at the time - I searched but couldn't find much detail on Eagle grinders - but this thread had inspired me to get going again!

I am very interested in the spindle arrangement on yours - I'm sure mine is not the original setup. On mine, the spindle has one deep groove ball bearing at the rear, and two taper roller bearings at the front. There is an endcap on both ends of the spindle housing, and two collars that are a press fir into the housing bores. The rear cap has a screw that acts on a blind plug to apply preload to the taper rollers at the front, by applying pressure to the rear bearing. Some pictures below.

caps.jpg

rear2.jpg

rear1.jpg

front.jpg

At the time, I bought 2 imperial angular contact bearings for the front, and a deep groove ball bearing for the rear, but I couldn't decide on a suitable method for applying preload - but I hadn't thought of using the spindle nut. Do you have a sleeve on the spindle to act on the front bearings? I would be interested if you had some more details on your setup, or a sketch would be really useful?

James

James,

On my machine the outer races are held tight in the housing by the front cover. The inner races are clamped against the shoulder on the spindle by the spindle nut and wheel hub. Pre-load is whatever is inherent to the bearing set. It's not perfect, but it's 'okay'.

If I get a chance I'll pull it out and take some pics for you.

Pete.

Thread: Collet runout. Is this normal
30/01/2021 20:54:09

That taper is running out from the body. The OD, thread, face and taper should have been machined on one operation. That one certainly has not, you can see it in the face chamfer. Most likely it was turned and threaded them moved to another machine for the taper to be turned or ground.

First thing I would do is blue up the rear mounting face to make sure it's flat and has no raised burrs around the bolt holes. Then I'd mount the chuck on the backplate and if it's hardened take a PCD insert and turn the taper. If it's un-hardened I'd use carbide.

To set up for turning, use your DTI on the inside face at the point where the cutting tip will be. Watch the dial as you turn the spindle and mark the point on the taper where the dial is mid-swing. This will be the closest you can get to the true collet angle. Now swing your compound round to the taper angle and run the DTI in the taper. Adjust the compound until you can run the DTI up and down the taper with no swing. Make sure your gibs are well adjusted and check it again. Now just paint the taper with a marker pen and turn it true until the pen is all removed. Remove the minimum required and remember that when cutting a taper this way the centre height of the tool is critical.

You might have to face and chamfer the front edge when you're done to make sure the nut doesn''t bottom out.

Thread: What inner spacer?
29/01/2021 23:24:07
Posted by Martin Connelly on 29/01/2021 21:45:24:

You need something with a similar coefficient of thermal expansion to the body of the roller.

Martin C

Edited By Martin Connelly on 29/01/2021 21:45:55

You don't, hence why you leave one bearing floating. Just like the rear spindle bearing on many lathes.

If the roller is a plastic like nylon it'll have 2-4x the expansion rate of aluminium so it's just not practical.

29/01/2021 17:39:15

Any metal tube would be fine for the spacer the main consideration is that the ends be as parallel as you can possibly make them. One bearing pocket should be a press fit , depth is the width of the bearing and fit this bearing first. The other pocket should be a light press or sliding fit and deep enough so that the inner race seats agains the spacer before the outer race bottoms out in the pocket, thus avoiding unwanted pre-load through the race. Press the second bearing on via the inner race and if you can, put an axle through the whole assembly for pressing to avoid the spacer tube being cocked whilst pressing.

Edited By Pete Rimmer on 29/01/2021 17:41:45

Thread: Machine corrosion protection
29/01/2021 11:30:01

Paul it all depends on the conditions in your workshop, and outside. I have a good amount of bare cast iron in my workshop and I don't use any surface protection at all becuse the temperature remains fairly stable. If I had an uninsulated roof I expect that I would be in a constant battle with rust.

Thread: Swinden Vice Problem
28/01/2021 18:41:06

Sounds like they have stretched the thread but I've no idea how as they clamp so well it should not be necessary. Probably using it as a press.

They are pretty easy to dismantle. Strip it down and inspect the thread.

Thread: What machine tools are these?
28/01/2021 12:42:20

The orange device looks like a compound rapid indexer. Pull the lever and you can turn the table one notch to index again. There may be several slotted or drilled plates nearby where it was stored, to swap out for different indexing options.

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