M and MG Class Machines Troubleshooting

1) Incorrect Needle – Try a larger Needle. Needles are available in sizes from #000 to #8. The larger the number the bigger the Needle.
 
2) Needle Carrier Stud is Loose – The Needle Carrier Assembly must be free to swing upon the Stud, but must not have any right to left lateral movement.

To adjust the Stud loosen the set screw, 4 9/32. Tighten the Needle Carrier Stud until it stops, then back it out 1/12 of a turn (30 degrees). Reference Needle Carrier Assembly.

3) Check the Looper Setting – Check that the Needle is not impacting or bending when it passes the Loopers. Reference the Looper Setting Instructions.
 
4) Needle Carrier Stud Hole is Worn – If a customer finds that he or she is continually readjusting the Needle Carrier Stud, it is a good indication that the Needle Carrier Stud hole is worn out. The machine should be shipped to the Merrow factory for service.

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1) Check Cutter Sharpness – Place a single strand of thread between the two blades. Turn the Handwheel by hand, and see if the thread is cut cleanly. If the thread is not cut cleanly, adjust, sharpen, or replace the Cutters. Refer Cutter Instructions.
 
2) Feed Dogs Set too Low – The Feed Dogs should be set so that the bottom point of the Feed Dog tooth is even with the top of the Needle Plate when the Feed Dogs are at their highest point of travel.
 
3) Too Little Presser Foot Pressure – Loosen the lock screw, and turn the adjustment screw clockwise a few turns. Retighten the Lock Screw.
 
4) Feed Dogs Worn – The points on the Feed Dog teeth are no longer sharp. They appear shiny and polished over. Replace the worn part.
 
5) Presser Foot Worn – The Presser Foot has channels or railroad-like tracks worn into its bottom surface. Replace the worn part.
 
6) Feed Dog Tilt – On certain fabrics it may be desirable to tilt the Feed Mechanism. Reference the Feed Mechanism.

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Holes in Fabric/Needle Tears
1) Replace Needle – Loosen the nut two turns. Remove the old Needle and replace it with a new Needle. Set the new Needle all the way back against the Stop Pin, and retighten the nut.
 
2) Incorrect Needle –

A) Try a smaller Needle. Needles are available in sizes from #000 to #8. The larger the number the bigger the Needle.
B) Try a Ball Point Needle. Merrow’s designation for Ball Point is “F”.

Ragged Edge (Fabric looks chopped, not cut)
1) Check Cutter Sharpness – Place a single strand of thread between the two blades. Turn the Handwheel by hand, and see if the thread is cut cleanly. If the thread is not cut cleanly, adjust, sharpen, or replace the cutters. Refer Cutter Instructions.

Poor Coverage on Edge
1) Increase the Stitch Count – Increase the number of stitches per inch by replacing the Feed Eccentrics (stitch cams). Use Eccentrics with a higher number. The number on the Stitch Cam represents the approximate number of stitches per inch. Reference the Feed Mechanism.

2) Use Additional Thread –

A) Use a heavier thread as the coverage thread.
B) On certain styles it is common to use more than one Cover Thread. 2DNR-1 and 3U are examples of this approach.

Loose Stitch
1) Check the Threading – Refer to the Threading Diagram provided with the machine, and ensure that the threading is proper.

2) Increase Tension of Thread – Turning the Tension Adjustment Nut clockwise to increase the tension. The standard setting is considered to be lock nuts on all tensions approximately even with the ends of the Tension Studs.

Edge Curling with Stitch – Too much fabric in stitch
1) Decrease Tension of Thread – Determine which thread is breaking, and decrease the tension on that thread. Turning the Tension Adjustment Nut counterclockwise decreases the tensions. The standard setting is considered to be lock nuts on all tensions approximately even with the ends of the Tension Studs.

2) Adjust Cutters – Move the Cutters to the left to reduce the amount of fabric in the stitch. Referernce Cutter Instructions.

Scratch on Fabric – Feed Dog Tracking on Fabric
1) Check for Burrs/Sharp Edges –

A) Check the Feed Dogs, and remove any burrs encountered.
B) Check for sharp edges on the Feed Dog slot(s) of the Needle Plate. Buff the sharp edges until smooth.

2) Too Much Presser Foot Pressure – Loosen the Lock Screw, and turn the Adjustment Screw counterclockwise a few turns. Retighten the Lock Screw.

3) Feed Dogs Set too High – The Feed Dogs should be set so that the bottom point of the Feed Dog tooth is even with the top of the Needle Plate when the Feed Dogs are at their highest point of travel.

4) Wrong Feed Dogs –

A) Fine Tooth Feeds should be used with light fabric.
B) Urethane Feeds should be used with delicate fabric.

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Oil on Fabric
1) Use the Proper Oil – Check to ensure that the proper grade or weight of oil is being used. Reference the List of Oils for Merrow Machines.
 
2) Clean the Machine – Check for and remove any lint or debris from around the Needle Carrier and Fabric Guard. Lint accumulating around the sewing area may become saturated with oil.

Oil on Table
1) Use the Proper Oil – Check to ensure that the proper grade or weight of oil is being used. Reference the List of Oils for Merrow Machines.

2) Clean the Machine – Remove any lint that has accumulated behind the Dust Shield and around the Feeds.

3) Replace the Oil Filter and Gaskets – If the oil filter is clogged with lint, it should be replaced. The Gaskets should be replaced at the same time. Reference Replacement of the Oil Filter.

4) Replace the Lower Pump – If the Lower Pump is not working the oil being delivered to the machine will not be returned to the reservoir. Replace the Oil Pump Plunger M-198-2, and the Oil Pump Plunger Spring 27-40. The Lower Pump is located in the rear of the machine behind a 3/4 inch diameter screw.

No Bubbler Flow
1) Replace the Upper Pump – If the Upper Pump is not working the oil is not being delivered to the machine. If one continues to run the machine in this condition, parts will burn and seize. Replace the Oil Pump Plunger M-198-2, and the Oil Pump Plunger spring 27-40. The Upper Pump is located in the front of the machine behind a 3/4 inch diameter screw.

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1) Replace Needle – Loosen the nut two turns. Remove the old Needle and replace it with a new Needle. Set the new needle all the way back against the Stop Pin, and retighten the nut.
 
2) Check the Threading – Refer to the Threading Diagram provided with the machine, and ensure that the threading is proper.
 
3) Check Cutter Sharpness – Place a single strand of thread between the two blades. Turn the Handwheel by hand, and see if the thread is cut cleanly. If the thread is not cut cleanly, adjust sharpen, or replace the Cutter. Refer to the Cutter Instructions.
 
4) Check the Looper Settings – Referring to the illustrations and descriptions provided help pin point the problem with the Looper Setting. Reference the Looper Setting Instructions.

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1) Replace Needle – Loosen the nut two turns. Remove the old Needle and replace it with a new Needle. Set the new needle all the way back against the Stop Pin, and retighten the nut.
 
2) Check the Threading –

A) Refer to the Threading Diagram provided with the machine, and ensure that the threading is proper.
B) Make sure the thread is coming off the spools freely without getting wrapped around the Thread Stand. 

3) Check for Burrs/Sharp Edges –

A) Determine which thread is breaking, and check for any sharp edges along its path of travel. Remove any burrs encountered, and buff the part smooth.
B) Check the Loopers for burrs. Remove any burrs and buff the Looper smooth. Take care not to dull the point in the process. 

4) Decrease Tension of Thread – Determine which thread is breaking, and decrease the tension on that thread. Turning the Tension Adjustment Nut counterclockwise decreases the tension. The standard setting is considered to be lock nuts on all tensions approximately even with the ends of the Tension Studs.
 
5) Problem with the Thread –

A) The thread might be brittle from a dying process or from age. Try another cone of thread from another lot if possible.
B) The thread might be too light a size/strength for the application. Reference the Chart for Merrow’s Recommended Threads. 

6) Check the Looper Settings – Reference the Looper Setting Instructions.

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