Shimming Techniques

[Ron LadenParticipant @ronladen17547]

If you haven't got one already can I suggest you get yourself a two insert 25mm end mill from ARC, I have one for my SX2P and it's one of the cutters I use the most on my machine. You can get larger diameter (ARC do a range of sizes) but I think 25mm is as large as I would run on a SX2.

Last week I did a similar job to yours cutting two flats 15mm long x 8mm deep on some 12mm EN8 flat steel bar. I took 1mm deep cuts across the full 15mm to the 8mm depth, no chatter and no horrible sounds.

As mentioned the 25mm size uses a pair of inserts, polished inserts for non ferrous and coated inserts for steel. I have found the mills top speed of 2500rpm good for alu and around 1750 for steel works well. Providing you don't go silly with the depth of cut the mill drives the tool very well with no issues.

For the SX2P I would really recommend getting one, I don't think you would regret it and soon find how much you would come to use it.

Ron

[Martin ConnellyParticipant @martinconnelly55370]

Joe Pie shows the nibble technique to minimise cutter engagement on a number of videos he has done. This one he uses it about halfway through at about 6:50. He is using the downward stop to get the correct depth for each plunge.

Martin C

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ron Laden on 26/12/2020 05:29:05:

If you haven't got one already can I suggest you get yourself a two insert 25mm end mill from ARC, I have one for my SX2P and it's one of the cutters I use the most on my machine. You can get larger diameter (ARC do a range of sizes) but I think 25mm is as large as I would run on a SX2.

Last week I did a similar job to yours cutting two flats 15mm long x 8mm deep on some 12mm EN8 flat steel bar. I took 1mm deep cuts across the full 15mm to the 8mm depth, no chatter and no horrible sounds.

As mentioned the 25mm size uses a pair of inserts, polished inserts for non ferrous and coated inserts for steel. I have found the mills top speed of 2500rpm good for alu and around 1750 for steel works well. Providing you don't go silly with the depth of cut the mill drives the tool very well with no issues.

For the SX2P I would really recommend getting one, I don't think you would regret it and soon find how much you would come to use it.

Ron

Thanks Ron – could you post a link to the one you mean, I can’t find a two insert cutter on Arc. I’m sure it’s there somewhere.

Cheers.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ron Laden on 26/12/2020 05:29:05:

If you haven't got one already can I suggest you get yourself a two insert 25mm end mill from ARC, I have one for my SX2P and it's one of the cutters I use the most on my machine. You can get larger diameter (ARC do a range of sizes) but I think 25mm is as large as I would run on a SX2.

Last week I did a similar job to yours cutting two flats 15mm long x 8mm deep on some 12mm EN8 flat steel bar. I took 1mm deep cuts across the full 15mm to the 8mm depth, no chatter and no horrible sounds.

As mentioned the 25mm size uses a pair of inserts, polished inserts for non ferrous and coated inserts for steel. I have found the mills top speed of 2500rpm good for alu and around 1750 for steel works well. Providing you don't go silly with the depth of cut the mill drives the tool very well with no issues.

For the SX2P I would really recommend getting one, I don't think you would regret it and soon find how much you would come to use it.

Ron

Thanks Ron – could you post a link to the one you mean, I can’t find a two insert cutter on Arc. I’m sure it’s there somewhere.

Cheers.

[Thor 🇳🇴Participant @thor]

I assume Ron is talking about these?
I have similar milling cutters (different inserts though) and I use them often.

Thor

[Ron LadenParticipant @ronladen17547]

Thanks Thor, yes thats the ones.

Dr, the R8 version is part number 060-282-00258 and the coated inserts (for steel) part number 060-282-1640M you need 2 off and also 2 off of part number 060-282-1604K (non ferrous).

The quality of the end mill and the inserts is excellent and the pricing is good to.

No connection with ARC just a satisfied customer.

Ron

[Dr_GMJNParticipant @dr_gmjn]

OK thanks both.

So if I was milling the end of some flat bar with the side of one of those, presumably I d take several cuts, incrementing downwards? What’s the maximum side milling cut you can take with one of those, in terms of vertical depth?

[JasonBModerator @jasonb]

Myself I would keep the 25mm insert tool for flat surfaces and use a 3 or 4 flute cutter for side milling. If you do use it for side milling on the SX2 then I would say 5mm vertical height cut and 1mm horizontal would be comfy on steel or iron.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 27/12/2020 10:06:32:

Myself I would keep the 25mm insert tool for flat surfaces and use a 3 or 4 flute cutter for side milling. If you do use it for side milling on the SX2 then I would say 5mm vertical height cut and 1mm horizontal would be comfy on steel or iron.

OK.

I notice the inserts for the 25mm tool have a R 0.8 on the tips. I think this might be ideal for cutting the tapered sides on the Princess Royal base castings (I previously used a 0.8 radius insert on my fly cutting tool to do the test piece, which looked fine). I could also presumably angle the bolted assembly and feed the tool down incrementally to finish the long ends to the end faces? The 25mm diameter would easily cover the depth of the sides that require tapering.

Thanks.

[JasonBModerator @jasonb]

Yes it will be nice for doing the ali sides, you can get other radii inserts as the basic shape is very common.

[Ron LadenParticipant @ronladen17547]

I never use mine for side milling, if its possible to turn the part so I can use the face of the endmill depending on size and shape of the part then thats what I do otherwise its 3 or 4 flute cutters as Jason suggests and side milling..

Its surprising what you can do with it though here is the shutter for the CHUKY engine, one piece 38mm x 12mm x 13mm of EN8 steel and all done with the 25mm endmill apart from the rad on the top of the block which I filed to shape.

A fairly small part 36mm long, 12mm wide and the block 8mm high, the shutter blade is 0.8mm thick and it turned out very flat, just needs polishing up which I will do by hand.

Edited By Ron Laden on 27/12/2020 14:25:17

[Dr_GMJNParticipant @dr_gmjn]

That sounds good. So the cutting edges extend enough to give about a 5mm cut on the sides if necessary?

[JasonBModerator @jasonb]

They extend further but being two flute you get a more intermittent cut which can start to knock a bit and much more than that would probably not suit the SX2P. I was using a 6 insert version today mostly for surfacing cuts but did not bother to change it for some side cutting10mm high x 1.5mm deep in aluminium at 1500rpl on the 63mm cutter.

[Dr_GMJNParticipant @dr_gmjn]

Would the Arc 40mm 4 insert version be better overall? I’d need a separate R8 Arbour (not available at present), but the less vibration/knock the better AFAIC…

[Peter Jones 20Participant @peterjones20]

Posted by Ady1 on 16/12/2020 23:17:22:

Concrete in pipes is used a lot in industry

Need to find a high quality version, then heat the pipe for a few days/weeks to expel water

Use hydraulic cement, it doesn't shrink and is waterproof unlike ordinary Portland cement

I'm working through replies, have you checked quill for movement side/side, etc?

If you have DTI mounted on table, how far does quill/head move when you torque on things?

Feed rate isn't too high for the cutter speed your using? (published speeds/feeds are generally for industry where material removal, tool life, surface finish and associated costs give the number of acceptable tool life)

Personally I tend to run a bit slower as I'm not pushing for production plus machine isn't really very rigid

 

Edited By Peter Jones 20 on 28/12/2020 06:47:52

[Dr_GMJNParticipant @dr_gmjn]

Peter – there’s no quill feed in an SX2P. I’ve not tried any measurements in-process.

As I said, I tried many feeds and speeds right down to almost zero on the last bit of brass I was working on and still got the same squealing noise from the cutter that I get on steel. Eventually at very, very low speeds I end up with a drumming noise from the flutes. As Jason said, in that particular case it was probably too much depth of cut, but again, as I said before with very small depths I still get the noise when the flank of the cutter is next to the previously machined surface.

Anyway, rather that wait for pre-cut shims that may or may not ever get sent, I’ve made a template to cut my own shims again. I’ve already cut the end of my finger somehow – the 0.005” stuff is just the right stiffness for that.

Ill set it up again with the widest shims I can, and leave it at that. There’s nothing else to adjust apart from the spindle bearings which appear to be OK. I suppose I could nip them up a bit – not sure how you do it though. Presumably a lock ring on the spindle somewhere.

[Martin ConnellyParticipant @martinconnelly55370]

Being vague with statements like "I tend to run a bit slower" is not a good idea. It is easy for beginners to overspeed and under feed when milling. Whilst it is perfectly acceptable to reduce the speed of the spindle to suit the needs of the operator and machine the feed must be matched to the rpm to ensure cutting not rubbing.

Regarding published feeds and speeds, I read that the design life of carbide inserts in industry is 15 hours and that is probably with flood coolant washing chips away.

Martin C

[Dr_GMJNParticipant @dr_gmjn]

So I finally got around to having another go at shimming the column.

I could only find one supplier of pre-cut shims for this size in the UK, and it was going to cost about £60 for the selection I wanted. Needless to say I cut my own shims, marking them as suggested.

I also ended up removing the column (as part of an unsuccessful attempt to rectify the dire backlash issues I'm having), and took the opportunity to lightly file the edges of the mating surfaces to remove any burrs, thoroughly inspected everything, and removed any imperfections. I then cleaned everything and re-assembled.

After three attempts with the new shims, over four points on the bed, I'm getting a maximum error of 0.001" over just over a 5" diameter (which is the largest continuous diameter I can get on the x-axis bed).

Is it worth chasing the 0.001", or do I leave it?

By the way, as before, three of the bolts needed shimming, and they were all different values., but it seemed much easier to get a result this time in terms of the shims corresponding to level corrections. I wonder if fettling the faces made a difference?

Any advice appreciated. Thanks.

[HopperParticipant @hopper]

Well done! Yes, fettling the burrs and dags off the mating surfaces will certainly make alignment easier through greater consistency. And give you a more solid base when machining.

One thou over 5 inches? A lot of home hobbyists could live with that on a small mill where inherent flexibility makes it all a little bit moot perhaps anyway. So personal choice really as to whether you live with it or try for that tad better. Maybe see how it goes in real life operation and then decide?

You could try just tightening the two bolts down on the one side a bit harder without changing shims. Sometimes this well get you that last half a thou that could make all the difference.

[Ron LadenParticipant @ronladen17547]

With 0.001" over 5 inches on a SX2P I would accept it and call it a day, its what I have on mine. Its up to you but don't get bogged down in chasing microns which I think on a small hobby machine is a waste of time and not necessary.

Allthough my machine measures one thou across 5 inches I recently milled a piece of bar 4.5 inches long and it ran out 0.0025" end to end which didn't surprise me.

 

 

 

Edited By Ron Laden on 21/01/2021 06:56:16

[Dr_GMJNParticipant @dr_gmjn]

OK thanks very much both.

Hopper – the bolts are all tight to the extent that I wouldn’t want to tighten them further. The ‘feel’ of them tells me I’d be risking over-tightening. And after working on cars and push bikes for many years I know how to strip threads…

I guess while I’m still in fettling mode, I’ve nothing to lose by adding a thou art one side and trying again. It seems like the side-to-side bolt spacing is also about 5”, so I guess 0.0005” should equalise the error. Shame I’ve got no shims that size!

[Dr_GMJNParticipant @dr_gmjn]

Could Aluminium kitchen foil be used as a shim?

[Ron LadenParticipant @ronladen17547]

Posted by Dr_GMJN on 21/01/2021 07:18:32:

Could Aluminium kitchen foil be used as a shim?

Don't be surprised if you break it down to chase for zero and find you get different readings, I would leave well alone but that's your decision.

[JasonBModerator @jasonb]

I'd leave it as is and see how things go on the next engine, can't get any worse than the one you have a already made.

As you know which way it leans you can make use of that when flycutting to give a light finish cut with the trailing edge.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 21/01/2021 07:33:32:

I'd leave it as is and see how things go on the next engine, can't get any worse than the one you have a already made.

.

Hopefully, I am I missing an in-joke

MichaelG.

[Author]

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