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Boxford 8" Shaper Problem

Shaper Won't Retain Length of Ram Stroke

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Alan Johnson 723/03/2019 10:46:40
63 forum posts
13 photos

My Boxford 8" shaper has developed a problem. I set the stroke to say 100mm amd with a cut of 1mm, the feed being on the return stroke, and the return stroke being "quicker" than the cutting stroke, after cutting - say 6mm, the bolt that adjusts the stroke "releases" and the stroke becomes maximum, which is about 200mm - on my metric Boxford.

I have tightened the stroke adjusting bolt "really tight," - I think too tight. The thread on the bolt is good, but I can't see the thread on the "crank gear sliding block," but I assume that if it were stripped, i wouuld not be able to tighten it as I can.

Have I missed something, or is it, as Alice said: "Curiouser and curioser."

Any suggestions welcome!

Clive Foster23/03/2019 11:10:40
1636 forum posts
45 photos

Similar self slackening adjuster issue in a completely different context was, eventually, found to be caused by marginal female thread depth. The bolt was bottoming out in the female thread at nearly, but not quite, tight enough clamping load. Fixed with a thicker washer.

Might be worth checking that the clamp washer under the bolt is still nice and flat. I have seen, and binned, ones similarly acting on a slotted component that had taken up a slight set into the slot so only the bit on the edge of the slot was really tight. I guess this effect is why the proper clamp washers are quite thick. Often made with the middle bit under the bolt even thicker with a taper out to the edge. Presumably to spread the loading and reduce any chance of sinking into the slot.

Clive

John Rudd23/03/2019 11:11:24
1364 forum posts
58 photos

Can you set the machine up as described then, without a work piece, set it going and watch what happens...?

if it repeats its issue, try again, but this time manually crank it and watch the bolt? You may see something you may not...and further investigation needed..

Alan Johnson 723/03/2019 12:09:19
63 forum posts
13 photos

Thanks Clive, I shall try tomorrow (20:04 at the moment for me).


Thanks John, that is a good idea. I shall check.I never thought of testing without a work piece in place.

Peter Simpson 123/03/2019 12:23:19
82 forum posts

HI Alan,

What material are you cutting, I have the same machine and it would struggle to cut 1mm over 100mm, if the material was mild steel..

Peter

Alan Johnson 723/03/2019 13:25:37
63 forum posts
13 photos

Mild steel. Perhaps I am asking too much of ther machine!

thaiguzzi23/03/2019 15:51:37
avatar
502 forum posts
104 photos

Not at all.

I have the same machine, and can hog 80 - 100 thou (2 - 2.5 mm in new money) no probs in steel.

The stroke problem certainly needs investigating further, i never need to hoik hard on mine to lock up adjustment.

I presume you are on the slowest of the 4 speeds?

Nick Taylor 223/03/2019 16:31:31
99 forum posts

Would like to see 100 thou in mild steel as well, well with a tool that was not so sharp that it blunts in a few passes... and with a finish that was worth the effort!

I had a similar problem with my Boxford, the adjustment nut felt tight but would slip easily under load. I found that if I rocked the crank handle back and forward say 1/8 of a turn as I tightened the nut it would tighten properly and hold correctly. I’ve stripped the machine down for other reasons (bearings) since then and saw nothing obviously out of order with the threads etc. I assume it’s an alignment problem, maybe some wear in the ID of the block.

not done it yet23/03/2019 22:14:06
2715 forum posts
11 photos

I don't know the machine, but depth of cut possible may be connected to speed of cut and feed rate. Even the angle of the cutter, too.

Comparisons of the same machine may not be a simple as just quoting depth of cut? Enlighten me, if otherwise.

Alan Johnson 724/03/2019 00:58:59
63 forum posts
13 photos

Thanks for all the responses and advice. I was cutting on the second speed is recommended in the Handbook for strokes of 4" to 6," but I reduced to the lowest speed, and the problem persisted. I shall try the suggestions later today.

thaiguzzi24/03/2019 06:22:43
avatar
502 forum posts
104 photos
Posted by Nick Taylor 2 on 23/03/2019 16:31:31:

Would like to see 100 thou in mild steel as well, well with a tool that was not so sharp that it blunts in a few passes... and with a finish that was worth the effort!

I had a similar problem with my Boxford, the adjustment nut felt tight but would slip easily under load. I found that if I rocked the crank handle back and forward say 1/8 of a turn as I tightened the nut it would tighten properly and hold correctly. I’ve stripped the machine down for other reasons (bearings) since then and saw nothing obviously out of order with the threads etc. I assume it’s an alignment problem, maybe some wear in the ID of the block.

If i'm roughing out 2mm DOC i aint bothered about surface finish.

Blunt tools are virtually unheard of in the TG shaper household.

And i can put a 2 thou DOC on a block of steel with a shear tool that would make a surface grinder blush.

Next?

Edit;

re the OP, are you tightening when the machine is in the correct position, ie the external feed adj wheel has marks on it that line up?

Edited By thaiguzzi on 24/03/2019 06:24:10

Nick Taylor 224/03/2019 08:10:34
99 forum posts

Next? You haven’t shown us this 100thou cut yet. By all means take your time to find the softest material you have.

Alan Johnson 724/03/2019 09:34:22
63 forum posts
13 photos

More testing this afternoon. Ran on second speed without making a cut with - no problem. Yes, adjusting crank setting with the marks aligned - as per the handbook. Then tensioned the crank setting - rocking the crank as suggested. Took a 0.5 mm cut with feed set to about maximum - OK. Then set the feed down to minimum , and a 0.2 mm cut - OK. Then adjusted the crank to have a 175 mm or so cut, again rocking the crank as I tensioned. Speed - lowest and 0.5 mm cuts, at maximum feed. No problems. Beats me! Looks like the suggestion of rocking the crank while tensioning works.

thaiguzzi25/03/2019 09:45:11
avatar
502 forum posts
104 photos
june - nov 2014 085.jpgPosted by Nick Taylor 2 on 24/03/2019 08:10:34:

Next? You haven’t shown us this 100thou cut yet. By all means take your time to find the softest material you have.

Er, i don't have to prove anything to you.

If you are unable to grind a tool for your machine to use it to it's full capabilities, it is not my fault.

As for soft materials, try delrin & brass next time, you should get a 4-5mm DOC.

Below is some real nasty stuff, flame cut, no-name steel, DOC was in the region of a minimum 60 thou (1.5mm in new money) i seem to remember.

2 blocks together to make 10 QCTP holders.

Next pic is the shear tool in use on the same material.

Have a nice day.

Edit; pics ar$e about tit, apologies.

OP, i like to use min ie low feed rates (1 click pref to 2 on the ratchet wheel) but make up for it with (supposedly unbelievable) DOC's. Try slow feed, bigger bite.

june - nov 2014 078.jpg

Edited By thaiguzzi on 25/03/2019 09:50:27

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