Making BXA toolholders

Michael C · Oct 6, 2006

Making up some BXA toolholders. Before I have cut the dovetail with a homemade tool using tnmg insert, it works but it hammers being a single cutter.

I was going to bite the bullet and buy a 60 degree HSS DT cutter from Enco but am unsure which one to purchase.Two choices that seem in the neighborhood are :
3/4" cutter diameter, 3/8" shank, 5/16" cutter width
or
1 3/8" cutter diameter, 5'8 shank, 9/16" cutter Width.

Any thoughts on if I can get buy with the smaller, less expensive one, or should I go with the 1 3/8" model.

Thanks
Michael

rklopp · Oct 6, 2006

I predict you will have chatter troubles with the smaller cutter. A 3/8" shank is awfully wimpy for the width of cut involved. If you have access to a shaper, use that and save your cutter money for a rainy day.

Think hard about how you will gage the dovetail before starting. It's not so easy, because the faces that need measuring are the slanted flanks and the *outside* faces, rather than the bottom of the slot. Simply measuring over dowels won't work, because they rest on the bottom of the slot, which is not necessarily a precision surface. That approach will work if you are first careful to get the slot depth correct. Do you have a nice-fitting BXA block to use as a master?

shapeaholic · Oct 6, 2006

Michael:
I am also in the middle of making some BXA holders. This time I am using a 3 insert dovetail cutter I made using TDEX (I think) inserts, like the ones used in Dorion tool cutter.
I'll try to post a picture later.

I made a batch of holders using a dovetail cutter like you are describing, and it did "hammer" but it got the job done.
Is the cutting edge of the insert above the center line of the holder? How much does the insert protrude from the insert?
The first cutter I made looked a lot like the one described here
http://www.dogpatch.com/bobp/shop/dovetail.htm

One tip I learned last time was to make the dovetail a little tight, and then remove small cuts from the contact face to get the handle on the tool post to line up at the 5:00 position. seemed like .001" would move the handle 10* or so.

Pete

rke[pler · Oct 6, 2006

One tip I learned last time was to make the dovetail a little tight, and then remove small cuts from the contact face to get the handle on the tool post to line up at the 5:00 position. seemed like .001" would move the handle 10* or so.

A couple of 1/4" dowel pins and an adjustable parallel will help you gage the dovetail. Put the pins into each dovetail and use the adjustable parallel as a clamp to hold them, then gage the parallel. You should be able to hit the desired size pretty much perfectly without pulling the part to check fit (or pulling the post to check fit, but that might be a good final check.)

Are the sides of the triangular inserts really straight enough for dovetail work?

dsergison · Oct 6, 2006

get the bigger dovetail.

inserts are plenty straight for this work.

Michael C · Oct 6, 2006

Thanks for the input guys. No shaper access, so I will make them. On my homemade holder I made the mistake of having insert cutting edge above center. What a rookie mistake, that probably accounts for a portion of the chatter. After seeing Pete's holder I may try making another one this weekend.

Thanks again all
Michael

rob daniel · Oct 6, 2006

I just picked up a small shaper just to try dovetails. I have a ton of cxa size holders but I need some QITP25 size holders. I was thinking of making them of 7050 or leaded steel. Since I have never used a shaper, I'm sure the project will be an education.

Toolbert · Oct 6, 2006

http://www.dogpatch.com/bobp/shop/dovetail.htm

Thanks for the plug

that's my website.

Michael did you mean to say TNMG? That's a neutral rake insert i.e. the edge is square to the face, so there's no relief to clear the cut when used as a milling cutter.

That is, unless you move it forward of the centerline, in which case it isn't cutting a 60 degree angle. The plane of the cutter face must go through the axis in order for a 60 deg cutter to actually cut a 60 deg angle.

Bob

Michael C · Oct 6, 2006

Yes, I did build my cutter with TNMG. Geez, its amazing it worked as well as it did. The toolholders I made fit well and the handle of toolpost is in 5 oclock position. Guess the lame get lucky sometimes. I will hunt down some of the TCMM inserts.

Michael

shapeaholic · Oct 6, 2006

Michael:
Here are a couple of pictures of my dovetail cutter:

I just finished cutting the dovetails on 3 new holders. I should be able to finish them tomorrow.
I'll post a picture when I'm done.

Pete

stephen thomas · Oct 6, 2006

I like Petes' cutter!

OTOH, as far as the original question, if the 3/8 shank x 3/4" cutter has a face width adequate to the job, it will work fine. I have and used to use, a lot of dovetail cutters. The 3/8" shank is buried in a normal R8 solid socket (EM holder). So the shank is supported right down to the top of the cutting edge by the holder. The smaller diameter cuts more freely in lower HP and less rigid mills. The 3/8" socket is shorter and projects less, so from the spindle out, the 3/8 shank offers more rigidity than the 5/8 in a 5/8" socket.

These cutters go defunct in two primary ways: 1.) Too heavy a cut for the spindle, chatter, and break the corners off the teeth. 2.) use a larger cutter than necessary to use a supposedly more rigid shank, hence wear out the bottom half of the teeth using them to make shallow dovetails.

Having made those observations, I do like the 1-3/8" x 5/8" shank style as an all around "one size fits most applications". But you can wear out 2 smaller ones for the same cost as one bigger one. Or if you chatter it and break the teeth, it is only half the price down the proverbial porcelain fixture....

smt

shapeaholic · Oct 8, 2006

Here are a couple of pictures of my efforts.
These tool holders have an extended nose for increased clearance, and the tool bit sits at 7* so I only have to grind the front and side, and top clearances. The back rake is taken care of by the 7* angle.

Pete

stephen thomas · Oct 8, 2006

Pete-

Nice holder. Why not take it a step further and put the side angle in the slot, then only the side clearance and nose angle have to be ground?

I made a reversible shaper tool holder that way a number of years ago, and it is handy for side cutting work where the toolhead is fed down (on the shaper). By reversible, the holder is a flat piece of barstock, with the same side angle on each end. So turned one end down, it is right cutting, the other end left cutting.

smt

spope14 · Oct 8, 2006

Nice - very nice. I have been dovetailing a bunch of 1" and 1 1/4 inch shank tooling over the last few months, used HSS dovetail cutters with 1/2 shank, worked well. I cheated a bit by actually undercutting the dovetail in a bit with an old carbide keyway cutter to clear out material as much as possible in the dovetail area, leaving as little stock as possible for the dovetail cutter. I really need to break down and get a real carbide insert cutter for this job if I keep at it.

Dowel pins and a go no go gauge block set up helped me do this right with my students, who were giev one 1 1/4 tool each to learn dovetail cutting.

Dieselrider · Sep 29, 2009

shapeaholic said:
Michael:
Here are a couple of pictures of my dovetail cutter:

I just finished cutting the dovetails on 3 new holders. I should be able to finish them tomorrow.
I'll post a picture when I'm done.

Pete

Say Pete, what are the inserts in your cutter? What angles did you use in your set up for your cutter? I am in the process of building a cutter now and am trying to determine the best insert and angles to use. Thanks

moonlight machine · Sep 30, 2009

I can understand making special holders. But not standard Aloris style holders as they are so cheap to buy, unless of course your time is not worth anything

Dieselrider · Sep 30, 2009

Actually, true Aloris holders are not cheap to buy at all. You can buy Chinese knockoffs pretty cheap but not the Aloris holders. Also you can make several at a time for a piece of steel about the price of two or three of the Chinese knock offs. If you have lots of money to donate to the Chinese economy, that's cool too. It's all good.

Darren UK · Sep 30, 2009

I'm only an amature....but I had a go at this over the last couple of days....

You can see my efforts here....http://madmodder.net/index.php?topic=1868.0

My first efforts failed....I know why...;-)

But my shaper jobs worked very well....

Dieselrider · Sep 30, 2009

Thanks Daren. I see the one fella that made a cutter, had used 60 degree inserts. The only problem I see there is your insert would cut the whole bottom as well as the whole side on the cut. I am not real familiar with all the variety of inserts but, I would think it better if the insert were say 45 degree so you would cut with the side but the bottom would only cut on the tip. I wonder if they make inserts between the 45 and 60 degree? I don't know if it is a big deal or not.

Darren UK · Sep 30, 2009

Yes it wasn't a very good design, I was just trying to use what I had to hand. I have some smaller tips on the way so will have another go and hopefully will make a better job of the next try. I finished my tool holder by the way. Very pleased with the outcome..!
http://madmodder.net/index.php?topic=1868.msg19281#msg19281

Making BXA toolholders

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