Member postings for Jim Gardner

Interesting replies and thank you all for them. Opinions are obviously varied, to the point that some people say they are easy to make, while others disagree.

Certainly for now, I will continue looking, specifically at Dickson tool holders.

I find that I could do with some extra tool holders for my Colchester Bantam. Despite searching the web for hours, all I get are general descriptions rather than what I need. I though I had found the correct one at Zoro Tools (Type 1 is a match in all dimensions they give, which does not include angles). Unfortunately they told me that holder was specific to their tool post.

I did find one article that suggested Colchester changed form their own post, to Dickson, and that may be what I have.

Could anyone help by telling me exactly what my tool holder is so I can search, or if they know of any retailer that sells them please?

Dimensions are, length 73mm, overall width 31mm, height 43mm. Tool slot varies between 18-22 height and 14mm wide.

Before I order, I’m curious; some of the cutters I have for this arbor are 0.5 inches deep/thick and others are 5 inches diameter. All have key slots including the thinnest ones. Can they all be used without a key and, if so, why do they have a key way in the bore?

Many thanks to you both. I will definitely be looking at those suggestions later.

Sorted.

Thank you for your inputs. I'm sure Bridgeport had a good reason, but to me it would have been easier if the chart looked like this,

I am finally getting to grips with my Bridgeport mill and have the need to use some slitting saw / face mills. I already have between 50 - 60 of the saws / cutters but have found that my R8 arbour has probably been used without the key in it, in the past and has got hot, causing wear. This means the tool does not run true.

I have looked all over the web for an R8 arbour to hold cutters with a 1" bore, with a key way, but cant find one. There are plenty without a key way, although I cant see how this would grip the tool well. I have also spoken to several tool suppliers who laugh when I say I need imperial not metric.

Does anyone know of a supplier that sells what I need, or, does anyone out there have one for sale?

I think you may be correct William. I have ordered a tachometer/revcounter so when that comes I will put a piece of tape on the spindle and get some readings.

Andrew, my switch definitely has 5 positions. Neutral, 2 speeds forward and 2 speeds reverse.

I am trying to get to grips with a Bridgeport mill with a J head. When altering spindle speeds there seems to me, to be 3 ways of doing it. a)The motor switch either position 1 or 2. b) High or low range on the mill. c) Altering the belt on the pulleys.

When looking at the manual it doesn't make a lot of sense to me. From the photo I can see that changing speeds from 67 to 115, or 115 to 180 or 180 to 275 could be done by moving the belt on the pulleys but it seems to say that speeds 67, 115, 180, 275,550, 920, 1500 and 2300 are all on Low Range and switch position 1, while all the other speeds shown underneath are on High Range and switch position 2.

Am I reading it completely wrong or are "Switch position 1 & SP 2" printed in the wrong place?

Edited By SillyOldDuffer on 24/08/2023 21:02:07

I have checked the run out on the bore of the spindle and found it to be a fraction under 1 thou. I believe when new, the acceptable run out was 3/10ths of 1 thou.

As a new spindle is £800 I think I will have to put up with it for now.

Would you accept say 8/10ths of a thou run out?

Thanks Pete and KWIL, excuse my ignorance but when you say try a die grinder, do you mean dropping the head, removing spindle, setting it up in a lathe, using a taper adapter and skimming it, or taking a very fine stone in a Dremel and lightly touching the inside of the spindle where the locating key hole is?

The problem I first mentioned is now solved but a much bigger problem has come to light which I will probably post a seperate question about tomorrow.

I have put a new collet locating screw in but collets still run out of true. Only about 1 thou on the side of the collet but at the edge of a 4 inch face cutter the run out -up and down- is huge.

Ever since I have been using it, the collet aligning screw on my Bridgeport mill has been broken off. I have just realised there is a tiny nub still poking out which could be touching the collet, so yesterday I set about removing the nose cap. This was extremely tight (after removing the set screw) and it took a 4 foot bar on a pin spanner to get it off. I have now cleaned up the nose piece and tried it in a friends mill. It screws in perfectly and almost by hand, but on my mill is is still very tight. I think the thread for the set screw may be protruding into the thread for the nose piece and the threads for the nose piece may be a bit rough / burred as well.

My problem is that I can't see any way to clean the threads. This is compounded by the very limited space (about 4mm) between the threads and the piece just inside of them.

Any ideas would be greatly appreciated.

Chris,

You're exactly right in that I am making a one off bolt and I will probably never have to make another one again, and I am doing it on a Colchester Bantam.

It is very rare that I ever have to make two of any threaded part (of the same dimensions) so buying a die or tap, go/no go gauges etc for every part I have ever made would be astronomically expensive. The same applies to full profile inserts for every thread/pitch I have ever, or will ever, cut.

This is why I purchased partial profile inserts, assuming (perhaps wrongly) that a Zeus book / Machinery handbook or the web would give me some way of working out how to get required depth etc using a PP insert of *** radius. Obviously I know there is more to it than that but I'm sure you get the idea.

Firstly, thank you all for the comprehensive answers. Secondly, sorry for asking as I seem to have opened a can of worms.

The good news is that at 10pm last night, after 3 attempts, I finally had a left hand thread, 1/2 inch Whitworth bolt. The bad news is, it took 3 attempts and to 10pm.

I can see (thank you Jason for the drawings) how different profile inserts make a difference to thread depth. What I cant understand is 1. Why manufacturers don't publish some type of chart or equation for applying to thread cutting. 2. How anyone copes with the trial and error method I used. Making a bolt is not a 5 minute job. 3.Why a full form/profile cutter would need to take any material off the top of the crest. A 1/2" bolt had an OD of 0.500". A 1/4" bolt has an OD of 0.250" etc. Surely it is what it is. Why would we need to make that OD less?

Lastly. It seems many people make a female first (in this case we can say a nut). If I made a LH thread 1/2" W nut to use as a gauge for the LH 1/2" W bolt I am making, how would I ever know how deep to cut the threads in the nut, in the same way I can't determine how deep to cut the bolt?

I intend to ring the very helpful suppliers today and ask them if there is a get around for this.

As with so many things in life, the more I learn, the more I realize how little I know.

Thanks again.

Thinking about it some more, it seems to me that depth of cut, is depth of cut regardless of full or partial profile inserts.

This is not my usual field so I am learning as I go, but it does seem strange that with all the tables/charts/equations etc. available, most people seem to measure thread depth by trial and error.

Unfortunately the female the bolt is needed for, is a spindle on a large electric motor that is far to big and heavy to offer up to the lathe.

And more to the point, what are "partial profile" used for?

Jason, you may have fund the problem. I looked it up and it is "partial profile". How then, would I work out depth of cut I need?

Howard, good point, but I don't think 2 degrees would make any difference to cutting depth would it?

Jason, It's a commercially bought/made 55 degree tool insert so I had assumed it would be the correct radius. If not, how would I ever know what my required depth of cut should be?