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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: Tools for Super 7
07/11/2019 12:06:34
Posted by Phil P on 06/11/2019 23:11:29:

I use a piece of 1/4" square "Stellite" in my tangential tool holder, I always sharpen it on the side of the wheel so I get a flat cutting face and then keep a really keen edge with an occasional touch up with one of those cheap diamond hand file thingy's.

Unless I need a specific shaped form tool for something, this is my "Go To" tool every time now. The surface finish it produces is superb. The Stellite tends to keep a sharp edge for much longer than regular HSS tool steel.

Phil

Stellite particularly has a 'favourite' orientation. If you look at a new piece it will have a small notch ground on one edge at the end. This should be the upper edge when being used conventionally as it's the strongest orientation.

Doesn't affect your tangential use just a FYI.

Thread: Inverters and stop switches
07/11/2019 11:27:03

At work we have numerous items of high-powered portable/pedestrian operated plant, probably a couple of hundred different machines from 1kw to 35kw nearly all 'high risk'. Many of them have three Estops but not one single one of them is fitted with an Estop that disconnects the incoming supply. All of them stop the motor and serve as a control interlock so that no control can be used until the Estop is released.

BTW I wasn't suggesting than someone SHOULD power a VFD with a NVR. It was just a suggestion for someone who was so paranoid about the above that they find it a distraction. I wouldn't find it necessary myself, at all.

06/11/2019 20:35:49

An Estop you wire into the control circuit, otherwise it's not and Estop it's a power disconnect, and not even a good one as it'll invariably leave neutral connected. if you desperately want the VFD to be instantly disconnect-able then feed it via a NVR.

Stopping in an emergency you want maximum braking and you won't get that by killing the VFD power.

Thread: building a myford super 7 from bits ?
05/11/2019 17:47:09

If the bed is straight and flat then the only thing that matters really is the headstock and tailstock centres are the same height. The underside of the headstock won't wear so it should be as aligned to the spindle as when it was new.

05/11/2019 12:47:09

You can chop & change most parts at will. My friend bought seven rusty machines and is renovating them all one at a time.

https://www.youtube.com/watch?v=TCpYsAIQgxo

Thread: What kind of diamond wheel i/ lap would the forum recommended?
05/11/2019 12:07:45

I use the lap wheels at 400rpm for sharpening carbide scrapers. You could probably go up a bit in speed for a 50mm wheel. Use some kind of solvent to cool/clean the disk as you use it.

Thread: Reaming - depth of cut
05/11/2019 11:50:20
Posted by Steve Sedgall 1 on 05/11/2019 09:15:05:

Just to add to the confusion the more material the reamer has to remove the bigger the reamed hole will be. Also the speed of the reamer/work will have an effect on overall size. Fast surface speeds will produce a hole bigger than slower speeds. As my old mentor used to say if you have a surface finish/size issue then check your roughing tool first.

An important fact that has caught me out more than once. If you cut so much that the chips pack the flute of the reamer, the hole is going to be over-size. I've even caused a reamer to cut over-size deliberately by packing one flute with blue paper towel. Turned a tight fit into a free-sliding fit.

Thread: How was this recording done?
04/11/2019 00:16:52

It says in the description right under the video:

Recorded with https://screencast-o-matic.com

Edited By Pete Rimmer on 04/11/2019 00:17:45

Thread: Pratt Burnerd 4 jaw Chuck jaw alignment
24/10/2019 11:20:36

I just checked, my spare jaws are PB but they are for a smaller 4-jaw having a .200 slot and 8tpi screws. The jaws in my 8" 4-jaws and a bit bigger with coarser screws.

23/10/2019 11:41:07

You should be able to grind an essentially brand new chuck without fear of the jaws cocking. If they do cock then they wouldn't be able to clamp anything effectively inside and outside without suffering problems.

22/10/2019 14:00:46

If you're going to grind then then turn a ring concentric on OD and ID and clamp it in the jaws on the ring's ID. Clock the ring in the 4 locations directly over each jaw and adjust until all read the same then you can grind them very gently at slow rpm.

Use the biggest grinding wheel you can sensibly fit in the hole so that when you dress it true you get the maximum amount of grinding before the wear on the grinding wheel reaches full span. You might do well to make a roughing pass, dress the wheel then take a very light finishing pass.

22/10/2019 00:43:31

I have I think 3 sets of 4-jaw chuck jaws of unknown provenance. Put up some basic dims of your jaws and I'll check the ones I have. In the unlikely event that one of those set match, you can have it.

20/10/2019 23:03:21

I think it's doubtful that it's the jaws themselves at fault. Is this one of those lightweight 4-jaw chucks with a shallow section and pockets cast in the back? They bend quite easily if you go daft with the chuck key. I would sweep the chuck face and then the jaw guides with a dial gauge mag-mounted to the cross slide. If the face of the chuck is dished then you can grind the jaws but they might not then be straight at another diameter.

Thread: Slideways oil
20/10/2019 16:05:49

Slideway oil here. Seems folly to use anything else unless I had none. Motor oil is better than nothing but slideway oil is made to maintain it's film under the flat ways without squeezing out, whereas motor oil is designed primarily to be pumped under pressure into tight gaps then run out so more oil can follow..

Thread: Limiting pressure to a gauge
16/10/2019 23:35:48
Posted by duncan webster on 16/10/2019 22:12:58:
Posted by Ian P on 16/10/2019 22:03:31:
Posted by Pete Rimmer on 16/10/2019 21:55:02:

Put a 30psi pressure relief valve before the gauge.

Where does the 'relieved' oil or pressure go?

Ian P

back into the sump, but the PRV would have to pass quite a bit of the pump flow to be effective, and that oil should be going round the engine, not back into the sump. You could put a restrictor in front of the PRV, but that would be prone to getting blocked and stopping the gauge working

If the oil pressure gauge isn't original could you put an end stop on the bourdon tube (so that it doesn't bend the needle) and simply let it hit this end stop at about 30psi. I doubt it would harm the gauge.

Quite, back to the sump. The restrictor should work fine. When the oil is cold and viscous it will reduce flow to the PRV (which will protect the gauge) and when the oil is hot the PRV won't open anyway so the restrictor is not utilised.

16/10/2019 21:55:02

Put a 30psi pressure relief valve before the gauge.

Thread: slidway lapping
16/10/2019 10:53:21

Don't do it.

Slideways need anything OTHER than a lapped surface. Just as you can wring two gauges together by the exclusion of any matter (including air) between them so can you wring two sliding surfaces by the same method and that includes the necessary lubricating oil. You end up with a high-stiction poorly lubricated movement joint that is prone to very high rates of wear.

Pete

Thread: VFD and screwcutting
15/10/2019 14:02:21
Posted by old mart on 15/10/2019 13:32:56:

The Schneider VFD which I bought for the mill has a default ramp up and down time of 3 seconds, this can be changed, but I don't know if changing it to 1 second stop would act like a brake.

That's exactly what it does, anything that stops the motor quicker than coasting is braking the motor. Your two considerations are that you don't overload the DC bus and you don't spin off the chuck.

15/10/2019 13:29:31

Any decent VFD will stop from the spindle screwcutting speeds in less than a turn especially in back gear, and less than quarter of a turn isn't hard to achieve if you're running up the a shoulder. Of course, having a VFD can let you increase your screwcutting speeds but another benefit is that you can use the speed control to back the speed right down as you approach the shoulder so that the stop is almost instant.

An external resistor is used to prevent the DC bus going over-voltage when braking. Easy to fit, easy to set up too, and pretty cheap.

It's difficult to find any reason not to use one TBH.

Edited By Pete Rimmer on 15/10/2019 13:30:10

Thread: Help with a boxford c
14/10/2019 12:27:25

The metal pin link belts not only work great but run smoothly and last a long time. The pins never touch the pulley so they shouldn't be an issue except aesthetically.

Removing the spindle because you don't like the idea of them is folly, as it can open up a whole new can of worms. It's common for the spindle bearings to be a very tight fit on the spindle so getting them back into adjustment can be very difficult.

Also be aware that whilst some spindles run on oil, many run in grease. Don't automatically assume that grease has been improperly used. Consult the manual for the machine before taking drastic action.

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