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Forum topic by Sawdust2012 posted 09-20-2014 11:48 AM 1126 views 0 times favorited 9 replies Add to Favorites Watch
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Sawdust2012

93 posts in 1177 days


09-20-2014 11:48 AM

I was helping a friend turn a bowl yesterday, and messed up. I turned a mortise on what would be the bottom of the bowl to mount it on when we turned it around to hollow the inside. In a classic “me” move, I turned it too large, about 4.25”. I’m having trouble finding G3 jaws to fit this opening. Would a cole chuck be safe? the mortise is only about 1/2” deep. I’ve also considered turning a jamb chuck and using his spur drive with a live center to hollow the vast majority of the bowl, then use cole jaws to finish the last bit. This bowl is about 15” diameter. Does anyone have any suggestions?


9 replies so far

View hairy's profile

hairy

2384 posts in 2997 days


#1 posted 09-20-2014 01:11 PM

I would turn 1/2” off the outside, and cut a new mortise. Also, 1/2” is pretty deep, 1/4” should do it.

Close your chuck jaws, measure the diameter, make your mortise just a wee bit bigger.

Cole jaws are for less than 1000 rpm, light cuts, not for hollowing.

-- stay thirsty my friends...

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#2 posted 09-20-2014 04:43 PM

Cut youself a plug to fit the botched recess, glue it in, and start over, carefully measuring so you don’t repeat that mistake again. When done hollowing the bowl, jamb chuck it and remove the repair…... Jerry (in Tucson)

-- Jerry (in Tucson)

View TheDane's profile

TheDane

4997 posts in 3128 days


#3 posted 09-20-2014 07:16 PM

No way would I consider using Cole Jaws. Jerry’s approach is the most likely to save your bowl.

I am more a fan of tenons or glue blocks than I am of mortises/recesses in the bottom of a bowl. Even with dovetail jaws and recesses, I have had workpieces turn on the jaws in the event of a catch which either throws the piece off the lathe or spins it enough that it no longer runs true.

In my opinion, you are much safer with either a tenon (which the jaws can really bite down hard on) or a glue block which performs the same function as a tenon. I am sure there are turners that have horror storied about glue blocks, but I have never had one fail. Glue block failures that I have heard about occurred when the glue block being used was either soft wood (Pine, Fir, etc,) or plywood. I make glue blocks with hard maple and use TiteBond I (red label original) that I let cure overnight.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#4 posted 09-20-2014 10:09 PM

I think Jerry has the best advice for your problem.

Whether you use a mortise or tenon to mount a bowl blank determined by size of the blank, moisture content, or finial design.

I have never had a failure using paper PVA glue joints, waste blocks and face plates before getting a chuck. I have use a waste block & CA glue in my chuck with no problem, but pretty apprehensive.

-- Bill

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#5 posted 09-22-2014 04:25 AM

Hey Dust, if you’re gonna be doing a lot of turnings, make yourself a go, no go tool. One size is the minimum that your chuck is ideal for a recess, and the other end of the tool would be the maximum. Anything in between would be perfect. It’ll save you time in the long run.

I use one for tenons. . It’s nothing more than a 6” long piece of 1/4” plastic with a cut out at each end to these sizes, 1 3/4” and 2 5/16”. When cutting tenons, slip it over the tenon. If it doesn’t fit on the larger size, keep cutting. If it slips over the smaller size, you done screwed up. It’s not supposed to slip over the smaller end.
Recesses would be about the same, but you would make a different type of jig…........... Jerry (in Tucson)

-- Jerry (in Tucson)

View TheDane's profile

TheDane

4997 posts in 3128 days


#6 posted 09-22-2014 02:12 PM

Hey Dust, if you re gonna be doing a lot of turnings, make yourself a go, no go tool.

Here’s one I made for my Nova G3:

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#7 posted 09-22-2014 02:44 PM



Hey Dust, if you re gonna be doing a lot of turnings, make yourself a go, no go tool.

Here s one I made for my Nova G3:
- TheDane

Well, heck, TheDane, that’s a mighty fine looking tool. Instead of talking about it, you have a picture, and that’s worth a thousand words. .

These things like this are like tips people ask about. You’ve been doing it or using it for so long, you pay no attention to the value until someone jogs the memory by asking…

My tool is a bit bigger and both ends are for tenons. I have never and probably will never use a recess. Jerry (in Tucson)

-- Jerry (in Tucson)

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TheDane

4997 posts in 3128 days


#8 posted 09-22-2014 04:53 PM

I have never and probably will never use a recess.

I’m not a fan of recesses/sockets either. I have busted out some pieces by over-expanding the jaws. Tenons, glue blocks and face plates work much better for me.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View moke's profile

moke

861 posts in 2241 days


#9 posted 09-22-2014 05:49 PM

Gerry, That is a great little jig and a good idea!!!! Thanks for sharing!!

Sawdust,
Use the glue block….we all have, it’s the safest for you and the piece.
Mike

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