Myford rear toolpost

Hi All

I recently purchased a rear toolpost to solve my issues with parting off.

It arrived from the UK, and works very well, but the tip of the parting insert sits about 2mm above centre, so work is not completely parted (it leaves around 4mm nipple).

I've contacted the supplier and they've offered a refund or replacement, but I'll have to post it back, which is reasonably expensive and slow.

Can someone let me know what the distance from top of cross slide to centre should be on an ML7 - I'm trying to work out if the issue is with my lathe or the toolpost. I've measured the distance from top of cross slide to parting tip and it's about 2.1".

If the issue is the toolpost I'll get a replacement, if the issue is my lathe, I'll see if I can get a couple of mm milled off the base of the toolpost.

If it's the tool post then milling it will make it right. If it's your lathe then milling the tool post will make it right. Seems to me the easy thing, and likely the right and fastest thing, would be to mill the tool post.

Pete

Thanks,

I don't have access to a mill and don't fell confident about doing it on the lathe, so will have to get an engineering shop to do it.

If the issue is with the toolpost it will be easier/cheaper to get a replacement.

Hi

As Peter has explained it does not matter which.To find your lathes centre height scratch a piece of flat bar supported upright with a square across the centre that you have mounted in your mandrel and then measure with your calipers.

Frank

Ahhh, no mill. That does indeed complicate things.

Pete

I had cause to measure the centre height of my ML7 from the top of the cross-slide a few years back and I got it to be 2.0625".

John

Stick in your 4 jaw, and face the 2mm off. Or fixture it to your faceplate. Easy peasy

Grind or file the top of the parting tool. When it is turned over for the rear tool post it will be lower. Just avoid the area close to the insert to avoid weakening it.

Martin

Grotto,

You do not need a milling machine for this job. Just mount the rear tool post sideways on the cross slide bottom face to the headstock and clamp it firmly ensuring it is square to the lathe axis. Check this by putting the face plate on and bring the bottom of the rear tool post firmly against it and tighten up. Then use a simple fly cutter (easily made) either in the 3 jaw or mounted on the face plate to remove the required amount of metal. It would be wise to take a bit more off than is calculated as the parting tool can easily be shimmed to get it at the best possible position.

The fact that a Myford 7 can be used for a lot of simple milling jobs like this explains why they have remained popular with "lathe only" owners over many decades.

The bottom of the toolpost isn't flat, so I can't face off 2mm in the 4 jaw.

I can't file the parting tool as it fits tightly in the slot in the toolpost.

I may be able to use a flycutter, will have to make one and have a try on some scrap first. I'm a bit nervous about taking some of the ridge which fits snugly in the slot on the cross slide.

File one side and pack the other to maintain the clamping effect.

Martin

Grotto,

It seems a pity, to me at least, that you have to put right their error and give yourself a lot of grief in doing so.

Why oh why do we as a group of the purchasing public repeatedly put right manufacturing faults that should simply not have happened. This is such a simple thing for them to make and yet they still make an a*se of it. These stories appear on this forum with depressing regularity and all manner of solutions are then proposed to overcome the deficiency.

Complain and make it stick

Brian

I think the problem is caused by the fact the insert blade cuts at a lower (or when flipped higher) point compared to a HSS blade. As a temporary measure you could get a HSS blade while you figure out how to fit the carbide one in.

I absolutely agree with Brian. as a general rule, that customers should not have to correct manufacturing faults but in this instance I feel that the item as supplied would be quite OK with a parting tool made from a HSS blank or with a shop bought conventional tool. The problem is that Grotto is using an inserted tool where the insert cutting edge is well back from the bottom edge of its holder. See his second photo.

Grotto,

You can cut off the bottom tongue and fly cut the base as suggested. You will just have to manually align the tool holder at ninety degrees with the machine axis.

You could consider cutting a step in the inserted tool holder to lower it by the required 2mm. On reflection this would probably be the quickest and simplest answer.

Wrong tool for the toolholder, not the toolholder,s fault.

Well if what you are parting has a bore it leaves no pip, if it hasn't then just face it off,not ideal but if it works?

My home made rear toolpost has the slot to hold cutter at a slight downward angle so by moving tool back or forwards centre height can be slightly adjusted up or down

Mick

I don't think it's the wrong tool for the job Ian H - it looks exactly the same as my RTP set-up in fact.

Grotto - I'd first ask the supplier to check their stock and see if the replacement was going to be any better.

Easy enough to do - just measure from the bottom of the tool holder block to the lower edge of the tool slot and ask them to do the same on one of their stock items. If the two are the same - then there is not much point in sending for a replacement. If theirs is measurably shorter - then you have a duff item and should just replace it.

If the replacement is going to have the same problem, then (in your circumstances) I'd ask for my money back.

The base will be hard for you to machine without a mill or shaper because of the T-slot extension..

One solution would be to just machine (fly-cut) the whole base flat and then replace the extension after machining with a bolt-on replacement piece but it's a lot of extra faffing around.

"Lowering the lip" will also make the slot wider and then you may not be able to grip the insert holder securely enough. The lip also has a small dovetail machined in it that (without a mill) you may find difficult to machine, not least because it's on the lathe's centre line (or in your case - just above it).

Replace it or just send it back in my view.

Regards,

IanT

Why send it back, either the supplier should pay postage or cut his losses and send a new tool holder (or tool) - If It is not as advertised you should not have to bear the cost of return postage. If the supplier is unwilling, let this forum know so that we can make an informed decision as to avoid him/her or not. If the supplier gives good service, let us know as well.
BobH

Ps - was the tool holder new - it looks a bit bashed about for "new stock"

Why send anything back. Their is no manufacturing fault in either the toolpost or the parting tool. It is the bringing together of the two parts that has created the problem. Engineering is all about bringing bit together.

If you were in the South east, i would happily bung the toolpost, or parting tool holder on my mill and do the job for you. Im sure you would find someone at you local model club equally ameanable to do a quick job for you. We are a friendly bunch really.

Hi there, all,

In answer to the OP's original question, and in case it comes in handy for anyone else, here's a scan from G.H.Thomas'  'The Model Engineer's Workshop Manual', page 240, Fig. 21.2, bottom RH corner.

GHT recommended ML7 owners to make their own version of this diagram and keep it handy.  I followed that advice and found that my ML7 dimensions agreed with GHT's within 3 thou.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 13/12/2015 13:21:00

Edited By Swarf, Mostly! on 13/12/2015 13:22:10